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Influence of sodium hydroxide (NaOH) concentration on the behavior of modified 9Cr-1Mo (P91) steel weldment with respect to stress corrosion cracking (SCC) resistance was studied in this work. Weldment of this steel was prepared using a shielded metal arc welding process using modified 9Cr-1Mo electrode followed by weld heat treatment at 1,033 K/1 h. Stress corrosion cracking experiments were performed at 473 K at a strain rate of 1 × 10−6 s−1 in millipore water (MP) (inert medium) as well as in 1 M, 2 M, 3 M, and 4 M NaOH medium. Ultimate tensile strength (UTS), yield strength (YS), and % total elongation (%TE) determined from stress-strain plots were found to decrease with increasing concentration of NaOH. The SCC susceptibility index (Iscc) evaluated using UTS and %TE was highest for the specimen tested in 4 M NaOH. The number density of cracks determined by optical microscopy increased with the concentration of NaOH. Also, it was higher in number in the base metal than in the weld metal. However, at highest concentration of 4 M NaOH, cracks were observed in the heat affected zone of the weld metal. Fractographic studies by scanning electron microscopic showed mixed mode from intergranular to transgranular cracking and vice versa at all concentrations of NaOH. Failure in the base metal was attributed to coarse precipitates, facilitating easy pitting at the precipitate/matrix interface. From the studies it was inferred that weld metal showed better resistance than base metal to SCC in 1 M to 4 M NaOH concentrations.

Failure of electronic components of printed circuit boards (PCBs) is a major concern, especially during storage. In the present study, we analyzed different modes of damages noticed on PCBs stored in coastal atmosphere such as leaking capacitors, white residues and attack around soldered joints. Fourier transform infrared spectroscopy, and pH measurements of the electrolyte from good and leaked capacitors indicated that the degraded electrolyte can cause capacitor leakage and subsequent failure. Scanning electron microscopy, energy dispersive x-ray analysis and x-ray photoelectron spectroscopy analysis of the white residue on PCB board showed the presence of phosphorus and oxygen as dendrites, formed due to the leaked electrolyte from capacitors on PCB. PCBs in continuous service with capacitor leak and white residue were also characterized. In this PCB, white residue was predominantly consisting of tin, oxygen and chlorine, which was formed due to corrosion of flux residue under high humid conditions. The damage around soldered joints of stored PCB board was found to be due to re-soldering, over heating which caused damage to the conformal coating and subsequent corrosion due to contaminants from flux residues. Based on the analysis of results, the probable mechanisms for the failure of PCBs are evolved, and the consequences for PCBs on prolonged storage and subsequent operation are also discussed.

In the present study, the efficacies of three different cationic and anionic ionic liquids (ILs) on biofilm formation on materials used in cooling water systems were evaluated. Two imidazolium based ILs; 1-Ethyl 3-Methylimidazolium tetrafluoroborate – (IL-E) and 1-Butyl-3-methylimidazolium chloride – (IL-I) with anionic fluoride and chloride groups and one piperidinium based IL, N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide – (IL-M) with fluoromethyl group as anion were used. The efficacy of these ILs were evaluated on planktonic and sessile cells of major biofilm formers in cooling water systems using Gram negative bacterium Pseudomonas sp. and Gram positive bacterium Bacillus sp. Further their effect on inhibiting biofilm formation on titanium and carbon steel surfaces were also evaluated. Results showed that planktonic cells of Pseudomonas sp. and Bacillus sp. were effectively inhibited by 25 ppm of IL-M and IL-E, respectively. For both bacteria, 50 ppm of IL-I was enough to inhibit and eradicate the sessile cell formation. Among the three ILs, IL-E was the best in inhibiting the adhesion of bacterial cells on Ti and CS surfaces. These results suggest that Imidazolium based ILs are effective in controlling sessile cell formation and eradicating mature biofilm as compared to piperidinium based IL. Further, Imidazolium based IL with fluoride anion (IL-E) was the best in inhibiting adhesion of these bacterial cells and thereby biofilm formation on material surfaces. This study establishes the feasibility of using ILs in cooling water system for bacterial biofilm control along with other conventional biofouling control methods.

The effect of Mo concentration on pit initiation rate and pit growth in austenitic stainless steels (SS) were investigated by electrochemical noise (EN) and confocal laser scanning microscopy (CLSM) techniques for the first time. We used 304LN, 316LN and 317LN containing different concentrations of Mo (0.02, 2.53 and 3.58 wt.%) for our studies. Using EN technique, initiation of pits and growth of pits were analyzed using Weibull and Gumbel distribution function, respectively. Pit depth was obtained using CLSM and the correlation between pit aspect ratio and Mo concentration were studied. Weibull probability plots showed that the Mo present in the alloy reduces the pit generation rates and improves the passivity. The plot for the pit size distribution using Gumbel distribution function showed the lowest metastable pit in 317LN and the highest in 304LN, suggesting the improvement in the pitting corrosion resistance due to Mo addition. The CLSM imaging showed maximum pit depth for specimen 304LN and minimum for specimen 317LN SS. Specimen 316LN SS showed intermediate pit depth. The depth of the pits observed in 304LN, 316LN and 317LN ranged from 80-100 µm, 30-40 µm and 20-30 µm, respectively. Alloy 317LN containing highest Mo concentration (3.58 wt.%) showed the lowest pit aspect ratio values followed by alloy 316LN with 2.53 wt.% Mo. These results indicate that Mo present in the stainless steel helps in arresting the pit growth and improve the resistance to pitting corrosion.

High-nitrogen-containing Type 316L stainless steels (SS) with 0.12% to 0.22% N are being developed as future structural material of fast breeder reactors because of their improved hardness and resistance to localized corrosion. However, stainless steels with higher nitrogen content are prone to intergranular corrosion (IGC) due to their tendency to get sensitized by enhanced precipitation of Cr2N. Thermomechanical treatment (TMT) of 6.5% cold-work and heat-treatment (1,323 K for 30 min) is evaluated in this study to enhance IGC resistance of 0.07%, 0.12%, 0.14%, and 0.22% nitrogen-containing Type 316L SS. The frequency of coincident site lattice (CSL) boundaries is found to increase with increase in nitrogen content in Type 316L SS. A maximum CSL increase of 35% was seen in 0.22% nitrogen containing stainless steel, as compared to samples containing 0.07% to 0.12% N. The effective grain boundary energy was the least (

In situ Raman spectroscopic studies on carbon steel specimens immersed in aqueous solutions showed the presence of Fe hydroxy salt, specifically green rust (GR), as the initial corrosion product in acidic, neutral and alkaline conditions. With increasing exposure time, GR was transformed to oxy-hydroxides, predominantly lepidocrocite (γ-FeOOH) in the upper layer and magnetite (Fe3O4) in the oxygen-deficient lower layer. The stability of GRs and their transformation are found to be dependent on the pH of solutions and anions present. The de-convoluted Fe peak in the Fe 2p3/2 region of XPS spectra of the corrosion products, formed on CS specimen immersed in tap water for 80 h, indicate the presence of lepidocrocite phase (γ-FeOOH), which was also evident from the laminar morphologies seen in SEM micrograph. The predominance of lepidocrocite over magnetite phase, in the presence of sulfate ions and in the low pH conditions, was in good agreement with the highest corrosion rate observed.

Round tensile specimens of modified 9Cr-1Mo steel were subjected to slow strain rate tests in 1-4 M sodium hydroxide (NaOH) solutions at 473 K to evaluate their susceptibility to caustic stress corrosion cracking (CSCC). The results obtained in NaOH solutions were compared with specimen tested in de-mineralized (DM) water. Secondary stress corrosion cracks were observed in all specimens tested in 1-4 M NaOH, the number of secondary cracks increased with increase in concentration up to 3 M. Tensile test data showed that ductility (%TE) decreased with increasing concentration of NaOH up to 3 M and nearly remained the same for 4 M NaOH. Time to failure was highest for specimen exposed in DM water and decreased with increasing concentration up to 3 M and remained constant thereafter. Crack velocity showed a trend of increasing velocity with increasing concentration of caustic media up to 3 M and remained same for 4 M NaOH. Laser Raman spectroscopic (LRS) analysis confirmed dissolution of protective magnetite and accelerated corrosion on the specimens exposed to 1-4 M NaOH solutions, leading to the formation of a number of oxides and oxyhydroxides. Fractographic studies showed typical surface oxide cracking with decohesions in all specimens. The studies showed that P91 steel is susceptible to CSCC in the concentrations from 1 to 4 M NaOH solutions at 473 K at a strain rate of 10−6 s−1. The evidence for dissolution of magnetite and the presence of decohesions indicated an important role for hydrogen in caustic cracking of P91 steel.

Here the effect of nitrogen on the intergranular stress corrosion cracking (SCC) resistance of sensitized Type 316LN stainless steel containing different amounts of nitrogen is reported. SCC studies were performed at 70% of yield strength. Double-loop electrochemical potentiokinetic reactivation technique was used to quantify degree of sensitization (DOS) that was correlated with SCC resistance. SCC time to failure increased from 220 h to 285 h with increasing nitrogen content from 0.07 wt% to 0.14 wt%, but decreased drastically to approximately 120 h at 0.22 wt% nitrogen (i.e., beyond N solubility limit), due to excessive precipitation of Cr23C6 and Cr2N and drastic reduction in the coincidence site lattice (CSL) boundary distribution from 48% to approximately 32%. Scanning electron microscope images showed mixed mode of failure.

A new sulfamic acid-based formulation is developed for the effective chemical cleaning of modified 9Cr–1Mo steel as a replacement for the conventional corrosive nitric acid (HNO3) and hydrofluoric acid (HF) mixture. The effect of sulfamic acid concentrations and inhibitor (2-mercaptobenzimidazole, MBI) on the metal loss during cleaning of modified 9Cr–1Mo steel was studied using weight loss and electrochemical impedance spectroscopic methods. The metal loss was found to increase with increase in acid concentration, but it was significantly lower with increasing inhibitor concentration, with an efficiency of > 90%. The corrosion rates of modified 9Cr–1Mo steel with 10% sulfamic acid + 2 mM MBI, 10% sulfamic acid without inhibitor and HNO3 + HF mixture were 1290, 6426, and 303,515 μm year−1 respectively. The optimal composition for efficient cleaning, with least base metal loss, was found to be 10% sulfamic acid + 2 mM MBI. Laser Raman spectroscopic (LRS) analysis of the corrosion products obtained during chemical cleaning process revealed that a protective chromium oxide film was formed during the cleaning with sulfamic acid + inhibitor as compared to iron oxide-based films with HNO3 + HF mixture and 10% sulfamic acid solutions.

We report fabrication of a regenerating superhydrophobic coating on 304L stainless steels, with superior corrosion resistance, using porous microcapsules made of calcium hydroxide as a core and a polymeric shell consisting of ethyl cellulose and poly methyl methacrylate. The synthesized microcapsules are characterized using optical, atomic force and scanning electron microscopic techniques, x-ray diffraction, Fourier transform infrared spectroscopy and immersion tests. The diameter of porous and permeable microcapsules ranges from 2 to 20 μm. On immersion of the coated surface in sodium stearate solution, the calcium hydroxide from the core diffuses through the pores of microcapsules and forms nanocrystalline hydrophobic calcium stearate needles pointing outward that repel water molecules. The maximum water contact angle obtained was 155.7° ± 2.05°. The micro-nanoscale roughness of the surface was evident from the AFM measurement. The cross-hatch tape adhesion test confirmed the strong adherence of the superhydrophobic coating. On damage of the superhydrophobic coating, the regeneration is achieved by immersing it in sodium stearate solution for 6 h where a 10° increase in contact angle is observed. Electrochemical studies in 0.1 M NaCl showed significant decrease in the passive current density and a delayed pitting, confirming better corrosion resistance of the coating in chloride environment.

This paper presents a method for enhancing the corrosion resistance of reinforcements through nanophase modification of fly ash concrete. A combination of natural and accelerated corrosion tests were performed to evaluate the corrosion resistance of reinforcements. The tests were conducted on four types of fly ash concrete specimens with and without nanoparticles designated as fly ash concrete with 40 wt% fly ash (FA), fly ash concrete with 2 wt% nano-CaCO3 (FAC), fly ash concrete with 2 wt% nano-TiO2 (FAT) and fly ash concrete with 1 wt% nano-CaCO3 and 1 wt% nano-TiO2 (FATC). Electrochemical measurements showed that reinforcements in nano-CaCO3 modified fly ash concrete (FAC) exhibited noble potential value, high polarization resistance and lower corrosion rate. Impressed voltage test also corroborate the enhanced corrosion resistance of FAC specimens, which was evident from the longer crack initiation time with minimum anodic current as compared to fly ash concrete without nano additives. Corrosion products of cover concrete showed a comparatively lesser amount of detrimental phases like lepidocrocite and goethite which was in agreement with the corrosion results. The least depth of chloride ion penetration indicated the effective plugging of pores by nano-CaCO3 particles that prevent diffusion and movement of chloride ions to surface of the rebar and thereby maintaining the passivity of the thin iron oxide layer around the steel rebar.

Summary Robert P. George is McCormick Professor of Jurisprudence and Director of the James Madison Program in American Ideals and Institutions at Princeton University. In “A Defense of Conscience in Healthcare ”, Dr. George reacts to Ethics Committee Opinion #385 of the American College of Obstetricians and Gynecologists (ACOG). Among other things, the opinion proposes that physicians in the field of women's health be required as a matter of ethical duty to refer patients for abortions and sometimes even to perform abortions themselves. Dr. George first responds to this imperative by challenging the nature of elective abortion itself as normal healthcare, based on the implicit judgment that pregnancy, when unwanted, is in effect a disease. In fact, the issues in dispute are philosophical; they cannot be resolved by science or methods of scientific inquiry. If this is the case, there is therefore no justification to compel morally sincere physicians who disagree with this judgment to violate their conscience or else leave the practice of medicine entirely. The ACOG statement fails to acknowledge the widespread debate about abortion in our society and the moral sincerity of pro-life practitioners.

The main objective of this study is to assess the long-term performance of Pt nanoparticle coated anodised Ti coupons which are used for electrochemical dissolution of spent mixed-oxide nuc...

The corrosion evaluation of buried cast iron pipe of fire hydrant system in a nuclear power station exposed to raw water for 30 years was carried out. The samples from cast iron pipe section were characterised by inductively coupled plasma atomic emission spectroscopy, optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and laser Raman spectroscopy. Metallographic examination revealed typical flake graphite microstructure with uniform distribution, randomly oriented graphite structure, rosette grouping, for pipes of different diameters. The presence of microbes in water side of the pipes and in contact with soil was seen. SEM examination revealed loose spherical deposits, rust layers comprising of iron oxide, silica and spherical nodules covered with network structures. EDS analysis of rust layers revealed the presence of Si, Ca, S and P apart from Fe and O. XRD analysis revealed that the rust on the surfaces comprised of SiO2 and Fe2O3. The results of the study indicated that the external corrosion of cast iron pipes was due to sand and gravel type of soil in contact with pipes. EDS elemental X-ray maps revealed regions rich in Si indicating localised graphitic corrosion. Detailed corrosion characterisation studies revealed that despite signatures of graphitic corrosion, microbes and rust formation, there was no substantial reduction in the pipe thickness, and hence, the service life of buried cast iron pipes can be further extended.

The present paper describes results of study on surface texturing of 304 L stainless steel with 1064 nm Nd:YAG laser having average power of 15 W, pulse width of 100 ns, scan rate of 20 mm/s and repetition rate of 2 kHz. Detailed surface characterization was done using microscopic techniques, XRD and water contact angle measurement. Nanosecond laser texturing generated a thin remelted layer with wavy pattern on the surface that enhanced micro roughness and hydrophobicity. XRD pattern revealed peak broadening indicating reduction in cold working effect and increase in grain size. Laser assisted texturing were successfully introduced on 304 L SS with 1064 nm wavelength and 100 ns laser pulses of energy 7.5 mJ. Electrochemical polarization studies in chloride environments and exposure to bacterial culture confirmed that this surface modification has contributed to enhanced corrosion resistance and antibacterial activity. Thus, by tailoring the wettability, surface roughness and texture; nanosecond pulsed laser texturing approach succeeded in imparting desirable properties for cooling water system materials.

During welding of 316L stainless steel (SS), heat-affected zone (HAZ) is susceptible to sensitisation and fusion zone is susceptible to pitting corrosion in stainless steel welds. High-nitrogen electrodes with 0.045–0.055 wt% C and with different Cr contents were used for welding of prototype fast breeder reactor components. As-welded and thermally aged (823 K for 2 h) weldments of type 316LN SS with different N contents made by arc welding were studied for localised corrosion. ASTM A262 Practice A and E tests and double-loop electrochemical potentiokinetic reactivation studies on as-welded and thermally aged specimens revealed the absence of sensitisation in the HAZ and in fusion zone. However, pitting potential of the weldments was found to vary with the concentration of N + Cr + Mo in fusion zone and found to be lower in the thermally aged samples. The correlation between weld microstructure, alloying elements and pitting corrosion behaviour has been discussed.

The phase compositions of nanoscale thick titania films on the titanium were determined using X-ray photoelectron spectroscopy valence band analysis for the first time, by deconvoluting the two-peak structure of valence band into five peaks and analyzing the relative peak area. The titania films of thickness varying from about 2 nm to 8 μm were obtained by the air oxidation of commercially pure titanium at different temperatures. The titania films formed on titanium for oxidizing temperatures up to 200 °C were amorphous, with thickness

A 400 l capacity nitric acid loop (NAL) test facility simulating inactive plant operating conditions was designed, constructed and evaluation of candidate materials was carried out for nuclear spent fuel reprocessing applications. Austenitic stainless steel coupons were exposed to flowing nitric acid medium at various temperatures in NAL. Assessment of critical components of NAL after 10,000 h operation revealed failure of titanium heater tubes and stainless steel heat exchanger tube sheet welds. Failure analysis and detailed characterisation of corrosion products on the failed tubes were carried out using SEM, EDX and XRD techniques. The brown colour corrosion product on titanium heater tubes comprised iron and small amounts of chromium indicating that failure of titanium tubes was due to deposition of corrosion products of stainless steel, leading to galvanic corrosion. Cracks observed on titanium heater tubes were attributed to hydrogen-induced cracking, resulting in severe degradation. Surface morphology and EDX analysis of the corrosion product on stainless steel heat exchanger tubes revealed dislodged grains from 304LSS and XRD analysis confirmed the deposit as stainless steel. Grain dropping occurred due to intergranular corrosion of 304L SS in nitric acid and deposition of the dislodged grains at the seal weld joints resulted in localised corrosion and failure. Based on the studies carried out, surface heaters instead of immersion heaters and periodic inspection and frequent removal of corrosion products from the nitric acid loop were suggested to mitigate such failures. Based on the results of the investigation, repair and refurbishment of the nitric acid loop was undertaken.

In this paper, a simple and economic method of superhydrophobic (SHP) surface modification of copper surfaces with water contact angle (WCA) of 147° ± 0.1° and roll-off angle of 5° is reported. SHP copper surfaces were synthesized by annealing copper foil in air and then coated with silica nanoparticles dispersed in silane solution. Scanning electron microscopy analysis of the SHP Cu surfaces showed the uniform distribution of spherical micron-sized CuO particles throughout the surface. Atomic force microscopy images of silane-coated surfaces showed increased valleys and peaks with higher root mean square and average roughness contributed by the silica nanoparticles. X-ray photoelectron spectroscopy results further confirmed the micron-sized CuO particles in the outer layer with silane containing silica nanoparticles, which contributed to the micro-/nano-roughness causing a phenomenal improvement in the WCA values. Electrochemical studies carried out in aqueous chloride environments demonstrated the corrosion resistance of superhydrophobic copper surface as evident from the shift in open-circuit potential values towards the nobler direction, increase in the charge transfer resistance and lower anodic current as compared with the fresh copper foil.

This study reports the enhanced chemical resistance of a blended concrete mix (CFNI) made with 40 wt.% fly ash, 2 wt.% nanoparticles, and 2 wt.% sodium nitrite inhibitor as partial replacement of cement against calcium leaching, acid and sulfate attacks. The concrete test specimens of four different compositions were fabricated and immersed in natural seawater, 3% sulfuric acid solution, and 10% magnesium sulfate solution for 120 days. Long-term chemical deterioration of the concrete systems is evaluated by assessing visual changes of the specimens and solutions along with the changes in percentage mass loss, compressive strength of the concrete, pH of the solution, and dimensions. The results indicate that CFNI concrete exhibits a superior resistance against chemical attack under all the three aggressive environments. Detailed chemical characterization of the specimens, carried out using XRD, FTIR, and thermogravimetric analysis, reveal a reduced CaO content, absence of deterioration phases like ettringite, brucite, and enhanced C-S-H content in the CFNI concrete. The addition of nanoparticles and inhibitors into fly ash concrete has lowered w/c ratio, increased surface pH, enabled conversion of soluble calcium hydroxide into insoluble calcium silicate hydrate, filled pores/voids, and reduced shrinkage and cracking. The compact microstructure of the CFNI prevented leaching and reduced the ingress of aggressive chemical ions into the concrete. Our results demonstrate that incorporation of nanoparticles and inhibitor into the fly ash concrete composition is ideally suited for the design of high-quality, low-permeable concrete structures that is the key for enhanced chemical resistance in natural and industrial environments.

Despite the progress made on superhydrophobic (SHP) coatings, a key challenge is the ability to fabricate mechanically robust SHP surface. Here, we report findings of the fabrication and characterization of a mechanically robust SHP aluminum (Al) surface with enhanced corrosion resistance and reduced biofouling. The new coating consists of a top hydrophobic layer of hexamethyldisilazane modified nano-silica (low surface energy material) and a middle connecting layer of hydrolyzed glycidoxypropyltrimethoxysilane that is covalently bonded to the SHP surface and hydrophilic aluminum substrate. XPS analysis of the SHP coating confirms –O-Si-CH3 groups. SHP coating showed multi-scale fractal morphology with a fractal dimension of 2.2, and asperities of length scale 32 and 630 nm. The maximum water contact angle (WCA) of the SHP surface was 170 ± 1.5° with a sliding angle ~1°. The SHP surface showed good self-cleaning ability for both the hydrophobic and hydrophilic contaminant. Less than 5% detachment of coating after cross-hatch adhesion test (ASTM D3359-09) and the retention of superhydrophobicity up to 150 cm in the abrasion test (ASTM D4060), confirm the mechanical robustness of the fabricated superhydrophobic surface. A two order reduction in the corrosion current density, and a corrosion inhibition efficiency of ~99% was observed in SHP surface compared to the bare sample. SHP sample showed poor adhesion to gram-negative and gram-positive bacterial strains and the superhydrophobicity was retained even after folding, shear abrasion test, cross-hatch tape adhesion test, and immersion in 0.1 M NaCl solution. Several new insights into the relationship between surface topography, fractal dimensions, self-cleaning process, anticorrosion and bacterial attachment are obtained. Our work provides a framework to develop mechanically robust SHP coating with enhanced corrosion resistance, and antifouling capabilities.

We propose a new method of quantifying the phases present in a binary mixture of nanopowder from deconvoluted valence band spectra using X-ray photoelectron spectroscopy (XPS). Polymorphs of iron oxide (γ-Fe2O3 and α-Fe2O3) and titania (anatase and rutile TiO2) nanopowders containing different weight percentages of the polymorphs were chosen for the present study. Pure iron oxide nanopowder (Fe3O4) was prepared by co-precipitation and was air annealed at 250 and 700 °C to obtain γ-Fe2O3 and α-Fe2O3 phases, respectively. In addition, anatase and rutile TiO2 were also used in the present study. A linear correlation between the percentage of the phase and the valance band peak area was observed in both the cases. The phase compositions of the nanopowder mixtures identified from the valence band spectra were compared with that of the X-ray Diffraction (XRD) data and the results were found to be in good agreement with each other. For nanoparticles of size >30 nm, no size dependent effect was observed in determining the phase composition but for particle size below 10 nm, size was found to have a detrimental role. These results showed that the phases of polymorphs can be quantified from XPS valence band analysis.

The paper focuses on a novel method for enhancing the biofouling resistance of cupronickel (90-10 Cu-Ni) alloy by surface modification involving sand blasting, pickling and coating with silane. After optimizing the experimental parameters for polishing, pickling and sandblasting in order to develop a hydrophobic surface, the surface morphology and the wetting properties of the modified surface were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM) and contact angle meter. The enhancement in resistance to bacterial adhesion was demonstrated by adhesion studies on Pseudomonas sp., the major biofilm former in marine environment. The silane based coating on the sand blasted surface of cupronickel alloy brought about two order reduction of bacterial attachment as compared to the control sample.

The present work focused on investigating the microbiologically influenced corrosion (MIC) susceptibility of ferritic steel–Zr-based metal waste form (MWF) alloy in simulated ground water m...

Titanium is known for excellent corrosion resistance for the sea water-cooled condenser material but susceptible to biofilm formation and bio-fouling, leading to deterioration in the heat transfer properties. Present study involves an attempt to use nanotechnology based surface modification of titanium to improve the antibacterial property and thereby resistance to biofouling. Synthesis of zinc oxide (ZnO) nano structures on Ti by a simple wet chemical method was achieved with the formation of nano structures under mild conditions in the absence of any seed, catalysts or surfactants. These nano structures were characterized using Field emission scanning electron microscopy which showed nano needle like structures. Grazing Incidence X-ray diffraction pattern showed a Wurtzite phase ZnO with strong peak at (002), indicating nano structure growth along the c-axis. Laser Raman Spectroscopy studies also confirmed the presence of Wurtzite crystals of ZnO nano structures. The antibacterial activity of these ZnO coatings with respect to gram negative bacteria, Pseudomonas aeruginosa sp. was investigated qualitatively and quantitatively. Epifluorescence microscopy and total viable count analysis have confirmed that ZnO nanostructures on the titanium substrate provided antibacterial activity against Pseudomonas aeruginosa.

The sensitization behavior of Type 316LN stainless steel (SS) with varying nitrogen content (0.07 wt% and 0.22 wt%) in 0% to 25% cold worked (CW) as well as in the as-received condition was evaluated. Time-temperature-sensitization diagrams were established for the cold worked Type 316LN SS (nitrogen content: 0.07 wt% and 0.22 wt%), using ASTM A262 Practice-E test. The time required for sensitization (ts) was found to decrease and critical cooling rates (CCR) increased up to 10% CW in the alloy with 0.07 wt% N. At higher CW, ts increased and CCR decreased. Similarly, ts decreased and CCR increased up to 15% CW in the alloy with 0.22 wt% N and at higher CW, ts increased and CCR decreased. To understand the sensitization behavior of Type 316LN SS with varying nitrogen content during thermal aging at 923 K for various durations, nondestructive electrochemical techniques like double loop electrochemical potentiokinetic reactivation (DL-EPR) technique and electrochemical reactivation technique (ERT) were adopt...

Superhydrophobic (SHP) coatings on titanium were developed using a two-step method involving anodization and coating with silane. The robustness of the SHP coatings was assessed by sonication and water impact tests. The adhesion of the coatings was evaluated by ASTM standard tape test. After evaluating the stability, the durability of superhydrophobic coatings developed on titanium was tested in seawater. The long-term immersion in seawater showed minimal reduction in water contact angle (WCA) after the immersion. Antibacterial activity of the SHP coatings after long-term exposure in seawater and bacterial pure cultures were also evaluated. The present study aims to evaluate the stability, durability and shelf life of the SHP coatings developed on Ti using silanes for long-term practical applications.

Critical components in reprocessing plants like continuous dissolver and centrifugal extractor demand austenitic stainless steels (SS) with good corrosion resistance coupled with high wear resistance in nitric acid medium. High nitrogen containing, impurity controlled, and vanadium-added 304LN1 (0.132% N), 304LN2 (0.193% N), and 304LN3 (0.406% N) SS with improved hardness were developed and corrosion studies were performed as per ASTM A262 Practice-A & C test and double loop electrochemical potentiokinetic reactivation test. The 304LN stainless steels were evaluated in forged, hot rolled, and hot rolled + heat treated conditions (948 K: 1, 10, 25, 50, 100, 260 h; 1,223 K: 1 h; 1,323 K: 1 h; and 1,473 K: 1 h). The study revealed good corrosion resistance for 304LN1 and 304LN2 SS as per ASTM A262 Practice-C test in sensitized condition (948 K/1 h). The degree of sensitization (DOS) and corrosion rates of high nitrogen 304L SS increased during sensitization heat treatment (948 K) done up to a certain aging d...

The corrosion of ferritic steel, a widely used structural material in the power and nuclear industries exposed to humid coastal environments, is a major concern. Here, we present a template-free one-step electrodeposition method for the fabrication of a robust superhydrophobic (SHP) coating on ferritic steel with excellent mechanical stability, enhanced corrosion resistance, and self-cleaning ability. By varying the electrodeposition time and potential, the micronanoscale hierarchical surface structures were optimized. The coated SHP surfaces were characterized by water contact angle measurement, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The coated surfaces showed a characteristic cauliflower morphology of cerium myristate with micronanoscale features. The maximum water contact angle achieved was 162.8 ± 2.4°. Shear abrasion testing showed good mechanical durability for the prepared coatings. The as-prepared SHP coating showed a five order reduction in corrosion current density (4.14 × 10

We report the early-stage corrosion of modified 9Cr-1Mo ferritic steel in aqueous environments at natural corroding conditions. Uniform, pitting, and crevice corrosion was observed in acidic sulphate, neutral chloride, and fresh water environments, respectively. In-situ laser Raman spectroscopy (LRS) studies revealed the formation of Fe3O4, γ−Fe2O3, γ−FeOOH phases, and stable heterogeneous corrosion products of γ−FeOOH and α−FeOOH in all media, except in an alkaline solution. A stable passive film, composed of oxide and oxy-hydroxides of chromium and iron, is formed in an alkaline solution. X-ray photoelectron spectroscopy (XPS) results confirm the presence of Cr and Fe oxide and oxy-hydroxides in all corrosion products and enrichment of Mn and Nb oxides on the corroded surface in neutral chloride solution, but only Mn oxy-hydroxide in acidic solution. Chloride ion in the corroded surface in neutral chloride solution indicates a chloride-induced corrosion attack. In-situ LRS, together with ex-situ XPS enabled the identification of all corrosion products formed on modified 9Cr-1Mo steel. The presence of laminar γ−FeOOH and acicular α−FeOOH phases are confirmed from the FESEM images. Our results indicate that except in alkaline solution, the corrosive ions deteriorate the integrity of native film on modified 9Cr-1Mo steel.

This work evaluated the performance of a novel nanophase modified fly ash based cement polymer coating over steel reinforcements in a corrosive environment. Five types of coatings were prepared with 100 wt. % Ordinary Portland Cement (CC), OPC replaced with 40 wt. % fly ash (CF), and CF admixed with 2 wt. % nano-CaCO3 (CFC), nano-SiO2 (CFS) and nano-ZrO2 (CFZ). Electrochemical studies were carried out under exposure to chlorides and the long term performance was evaluated by impressed voltage test. The microstructure of the developed coatings and chemical composition of corrosion products were analyzed using SEM, XRD, and LRS. The instantaneous corrosion rates of CFC, CFS, and CFZ coated rebars were found to be notably lower than CF coated rebars. The accelerated studies using impressed voltage test indicated a significantly longer initiation time for cracking in nanomaterials incorporated coatings than the conventional cement polymer coating. The evaluation of electrochemical parameters like open circuit potential, corrosion current, and polarization resistance showed that the addition of nano-ZrO2 significantly enhanced the corrosion performance of cementitious coatings as compared to other nanomaterials owing to its better dispersibility, without aggregation in cementitious product, which was further confirmed from the particle size distribution measurement using dynamic light scattering technique. The XRD patterns and laser Raman spectra results confirm negligible corrosion products on CFZ coated rebars. The visual inspection of rust formation and weight loss measurements of CFZ coated rebars, subjected to salt spray and chemical resistance tests corroborated its long term durability in chloride-rich environment. Our results suggest the important benefits of nanomaterial incorporated fly ash cementitious coating on rebars in corrosion protection.

The urge to reduce the carbon footprints from cement production warrants the development of more sustainable approaches in the construction industry. Towards this, the long term corrosion resistance of the embedded steel rebar in a novel ternary-blended reinforced concrete system with 56 wt% Ordinary Portland cement (OPC), 40 wt% fly ash, 2 wt% nanomodifiers, and 2 wt% corrosion inhibitor (referred to as CFNI) was studied by chemical and electrochemical tests in a simulated chloride environment for 180 days. The performance was compared with three other concrete systems (CC (100% OPC), CF (60 wt% OPC and 40 wt% fly ash) and CFN (58 wt% OPC, 40 wt% fly ash and 2 wt% nanomodifiers). The electrochemical results indicated a significant enhancement in the corrosion resistance of steel in the CFNI concrete as compared to other systems. A five times higher value of polarization resistance (Rp) is obtained in CFNI, as compared to the control concrete, indicate the better resistance of CFNI. Further, in CFNI specimen, the chloride ingress rate was significantly lower and the Field Emission Scanning Electron Microscopy (FESEM) images showed no microcracks or pores at the corroded concrete-steel interface of CFNI specimens. The apparent diffusion coefficient (Dcl) of the concrete system was determined using the bulk diffusion test and chloride profiling. The value of Dcl for CFNI concrete was found to be one order less in magnitude than other concrete specimens, indicating the enhanced resistance against chloride attack. These results show that CFNI concrete is a promising ternary-blended concrete mix to achieve long corrosion-free service life for the structures in aggressive chloride environments.

Purpose The purpose of this paper is to study the metal-Microbe interaction playing a crucial role in microbiologically influenced corrosion (MIC) and biofouling of materials in cooling water systems. Treatment regimens should be planned based on this understanding. Design/methodology/approach Attempts were made in the past decades to characterize and understand biofilm formation on important power plant structural materials such as carbon steel (CS), stainless steel (SS) and titanium in fresh water and in seawater to achieve better control of biofouling and minimize MIC problems. Findings This report presents the results of detailed studies on tuberculation-formed CS because of the action of iron-oxidizing bacteria and the effects of algae- and bacteria-dominated biofilms on the passivity of SS. The preferential adhesion of different bacterial species on SS under the influence of inclusions and sensitization was studied in the context of preferential corrosion of SS weldments due to microbial action. Detailed characterization of biofilms formed on titanium (the likely condenser material for fast breeder reactors) after exposure for two years in Kalpakkam coastal waters revealed intense biofouling and biomineralization of manganese even in chlorinated seawater. Studies on the effectiveness of conventional fouling control strategies were also evaluated. Originality/value The detailed studies of different metal/biofilm/microbe interactions demonstrated the physiological diversity of microbes in the biofilms that were formed on different materials, coupling their cooperative metabolic activities with consequent corrosion behaviour. These interactions could enhance either anodic or cathodic reactions and exploit metallurgical features that enhance biofilm formation and/or the capacity of microbes to mutate and overcome mitigation measures.

Corrosion protection coatings were developed based on a hybrid self-assembled nanophase particle process (HSNAP) for the localized corrosion resistance of modified 9Cr–1Mo steel in 0.05 M NaCl solution. The coating sol was prepared using silane-zirconia precursors and a polymeric crosslinking agent. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to study the morphology and composition of the coated specimens, respectively. The thickness of the coatings was determined by a thickness gauge meter and Raman imaging analysis. The corrosion resistance of coated specimens was analyzed using electrochemical impedance spectroscopy, and it was observed that HSNAP-coated specimens showed superior resistance to localized corrosion than the as-received specimens in chloride medium.

The present work involves development of noble metal nanoparticle coated Ti based electrode for application in severe corrosive environments. The etched Ti substrate was coated with noble metal nanoparticle via a seed mediated hydrothermal reduction method. Advanced surface characterization techniques elucidated that this two step synthesis method generated a uniform and highly dispersed nanoparticle coating on Ti which is essential for application in severe corrosive medium. The enhanced activity for methanol electro-oxidation compared to polycrystalline Pt proved the excellent electrocatalytic activity of as synthesized Pt nanoparticles coated Ti electrode. The adhesion strength of the coating on the Ti substrate was found to be excellent with a rank of 5A as per ASTM standard. The long term durability of Pt nanoparticles coated big cylindrical Ti mesh with 164 cm2 surface area was tested by employing it as anode for electro-oxidation of Ce in 11.5 M nitric acid under an applied operational current density of 9 mA/cm2 for 1000 h. Only 1 V increment was observed even after 1000 h confirming the excellent durability of this electrode. SEM and elemental mapping of the surface of coated electrode after 1000 h exposure in severe corrosive nitric acid further confirmed uniform dispersion of Pt on the surface and absence of delamination.

An attempt was made to explore the electrochemical behavior of Titanium (Ti) condenser material under seawater biofilms. The Ti specimens with seawater biofilm were subjected to microscopic examinations and electrochemical studies such as cyclic voltammetry (CV), electrochemical impedance spectroscopy, open circuit potential monitoring and anodic polarization. The CV curves of Ti specimens with 15 days old biofilms showed characteristic redox peaks with high cathodic current indicating the electroactive biofilms. Similarly impedance spectra clearly showed two time constants with decrease in charge transfer resistance and increase in capacitance as the biofilms growth increased on the Ti specimens. Polarization curve showed the ennoblement of corrosion potential and increase in passive current with the growth of biofilm on Ti. Based on these data, a possibility of Ti passive film integrity loss by electroactive seawater biofilms has been discussed.

Lotus leaves are a typical example of superhydrophobic surface. Numerous studies have confirmed that surface morphology possessing micro- and nanoscale roughness along with a low surface energy material coating leads to apparent water contact angle (WCA) ⩾150°. In nuclear power plants, modified 9Cr–1Mo ferritic steel is the favoured steam generator tubing material. During transit, storage and installation, SHP surface on modified 9Cr–1Mo ferritic steel can impart good corrosion resistance to retain the integrity of the specimen during operation. In this study, SHP surface of modified 9Cr–1Mo ferritic steel with a WCA of 150±1° was successfully achieved by polishing, etching, perfluoro octyl triethoxy silane coating and baking. The WCA and contact angle hysteresis were measured. The surface morphology and the composition were characterised by atomic force microscopy and attenuated total reflection–infrared spectroscopy respectively. Superhydrophobicity and its related theories are also discussed in this paper.

45S5 Bioglass with a mean particle size in the nano regime were synthesized and fabricated with rGO sheets using three different strategies. The fabricated nanocomposites were analysed for their bond formation and defects. Morphology, size and distribution of n-BG particles on rGO were visualised. An attempt to understand the superoxide anion production by n-BG particles, rGO and its nanocomposites was made.

Three different types of nanophase modified fly ash mortar specimens were prepared to evaluate the antimicrobial properties in seawater. Two percentage of OPC was replaced by 50-80nm and 50-70nm sized TiO 2 (FAT) and CaCO 3 (FAC) nanoparticles respectively. In the third type of mortar specimens a 2% of the OPC was replaced by mixture of both nanoparticles in same ratio (FATC). All the nanophase modified specimens along with FA specimens were cured in water for 28 days and exposed in seawater for a month. Specimens were withdrawn at different intervals for post-exposure analysis. Detailed microbiological characterization involving density of total heterotrophic aerobic bacteria, slime formers, anaerobic bacteria, manganese-oxidizing bacteria, fungus, sulfur oxidizing bacteria and biofilm imaging using epifluorescence microscopy, total dissolved and suspended solids in biofilm were carried out. pH reduction of the surface of the specimens were measured by flat surface electrode. Results demonstrated lesser pH reduction and enhanced antibacterial activity on the surface of FAT and FATC mortar specimens under the influence of TiO 2 nanoparticles.

In this investigation, we report the development of bioactive glass (BG) and reduced graphene oxide (rGO) - bioglass nano hybrid (G-BG) thin films over anodized TiO2 nanotubes via electrophoretic deposition method (EPD). Different parameters such as concentration of particle loading (BG and G-BG), concentration of sodium alginate (Na Al) - anionic charge donor and polyvinylpyrrolidone (PVP) - binder, voltage, deposition time and annealing temperature were analyzed. X-Ray Diffraction (XRD) studies revealed phases of anatase in anodized substrates, whereas in BG thin films along with anatase, combeite phase of bioactive glasses were also found. In the case of G-BG thin films in addition to anatase and combeite phases calcinate phase was also observed SEM results exhibited the anodized TiO2 pore diameter to be around 100 nm, whereas the thickness of the nanotube layer was found to be approximately 6 μm. The SEM analysis on BG and G-BG thin film layers over TiO2 layer was observed to be 2 μm in thickness. Due to the dissociation of sodium ions from BG thin films, cell lysis was observed to higher in hemocompatibility, antibacterial activity and cell proliferation analysis. This phenomenon of BG thin films were advantageous in antibacterial activity but deleterious in hemocompatibility and cell proliferation. However, the calcite phase in G -BG thin films suppressed this activity and showed better hemocompatibility and cell proliferation of MG-63 cell lines. From this study, it is evident that incorporation of rGO in BG thin films enhanced the HCA formation, hemocompatibility and MG-63 cell proliferation.

In this paper, we report the enhanced biodeterioration and biofouling resistance of a modified fly ash based concrete, formulated by the addition of fly ash, nano-TiO2, nano-CaCO3, and corrosion inhibitor into conventional concrete. After six months of exposure in natural seawater, the modified fly ash based concrete showed a three to four order reduction in aerobic and anaerobic bacterial density, which was confirmed by epifluorescence and confocal microscopic investigations. The FESEM micrographs showed a characteristic surface morphology with uniform distribution of more calcium silicate hydrate (CSH) gels and aluminate hydrates, absence of discontinuities, pits, and cracks on the modified concrete surface which helped to resist the ingress of aggressive ions from seawater. The comparatively lesser reduction in surface pH, low water/cement ratio, better bulk thermal properties, and low surface roughness facilitated the improvement in the antimicrobial and antifouling properties of modified concrete. The addition of nanoparticles and inhibitor increased the hydration of cement resulting in the formation of more portlandite which got converted into more hydration products, producing a pore free morphology. The inherent photocatalytic activity of nano-anatase TiO2 and bactericidal activity of sodium nitrite due to the presence of reactive nitrogen species (RNS) together enhanced the biofouling and biodeterioration resistance.

We report an anomalous enhancement of corrosion resistance and antibacterial property of CP-Ti surface in the presence of a uniform defect-free nanoscale (∼15 nm) rutile titania film. Selective absorption of blue light (∼410 nm) due to matching photon energy with the film band gap, drastically enhanced the electron-hole pair generation, recombination time and the photocatalytic activity. The corrosion resistance of the rutile phase titania films is found to be better than the amorphous films and strongly dependent on the film thickness and surface morphology. The impedance data accounts well for the dual layer structure with an outer barrier titania and inner substochiometric oxide layer.

We report a simple, rapid, inexpensive and eco-friendly method for fabricating super hydrophobic (SHP) titanium surface using ethanolic solution of myristic acid and HCl through simultaneous anodization and adsorption. The coating performance is optimized by varying the anodization potential, acidic concentration and anodization duration. The prepared superhydrophobic surfaces are characterized using water contact angle (WCA), Fourier transform infrared (FTIR) spectroscopy, Laser Raman Spectroscopy (LRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). At an optimal anodization potential, the coated surface is found to be densely populated with hierarchical micro-nanoclusters of titanium dioxide adsorbed with myristic acid, exhibiting a maximum WCA of 176.3°±1° with a sliding angle of 1°. SHP surface showed surface features with layered ridges decorated with submicron sized aggregates. The liquid-air area fraction on the prepared SHP surface is ~0.97, with an asperity slope ψ > 71°. SHP surface exposed to microbial cultures for 48 h showed 50% reduction in bacterial adhesion. Bouncing dirt removal and bouncing of drops suggest better cleaning efficacy and excellent water repellency of the SHP surface. The fast fabrication, excellent anti biofouling, chemical and mechanical stability of the SHP coating offer interesting applications, and also opens up new ways for creating stable superhydrophobic titanium surfaces with excellent self cleaning characteristics.

The global warming gas, CO2, is liberated when clay and limestone are crumbled for the production of cement. About 8–10% of the universal CO2 emissions are emitting from the cement factories. With concerns arising over environmental issues associated with cement usage, it is the need of the hour to reduce its consumption. Fly ash, the waste material from thermal power plants, is a widely used supplementary cementitious material that extends the life of the concrete structures. The intervening of nanotechnology into construction industry has provided wider opportunities to better the performance of concrete in rigorous conditions, especially acids and alkali environment. This work endeavours to study the effect of surface-modified fly ash concrete through the addition of nanoparticles against sulphate attack and calcium leaching. Nanophase modification was performed by integrating nano-TiO2 and CaCO3 for enhanced durability and corrosion resistance. Four types of concrete mix, namely fly ash concrete (FA), FA with 2% TiO2 nanoparticles (FAT), FA with 2% CaCO3 nanoparticles and FA with 2% TiO2:CaCO3 (FATC) nanoparticles, were designed and casted as cylindrical concrete blocks. The specimens were immersed in 1% sulphuric acid solution and sea water to study the resistance of concrete against sulphate attack and calcium leaching, respectively. Results showed that nanophase modification of fly ash concrete improved the resistance to sulphuric acid attack and calcium leaching. Among the nanophase-modified specimens, FAT and FATC specimens showed superior performance.