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To investigate the effect of acid corrosion on the mechanical properties of the Diorite specimens, obtained from Qian Chang Copper mine in China, the specimens were first saturated in neutral water and acid solutions with pH values of 3 and 5 for 49 days. Then, electronic scanning tests, uniaxial compression tests and triaxial compression tests on the saturated and dry specimens were sequentially performed. The results show that the acid corrosion, causing micro damages on the specimens, decreased the unixial compression strength, the triaxial compression strength, the cohesion and the internal friction angle. In addition, the decrease degree was negatively to the pH value. Third, the acid corrosion promoted the ductility of the specimens.

In the present investigation, thin layer activation technique has been employed to study the effectiveness of an amine derivative compound, namely hexamethylene tetramine (HMTA) for corrosion inhibition of carbon steel in acid solution. The corrosion studies have been performed in 1 mol dm−3 HCl containing different concentrations of inhibitors. Inhibition efficiency of HMTA at different experimental conditions has been estimated. It was observed that at ambient condition, 500 ppm HMTA effectively inhibits acid corrosion of carbon steel with an inhibition efficiency of 89.8%. The inhibition efficiency was found to be altered by increase in the temperature of corrosive solution.

The relationship between the specific surface area (SSA) of rust and the electrochemical behavior of rusted steel under wet–dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O2 into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O2 and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.

Effects of W and Mo additions on wet-dry acid corrosion behavior of low-alloy steels under different O2 concentrations were investigated. The results showed that W and Mo-containing steels presented excellent wet-dry corrosion resistance under O2 concentrations of both 1 and 5%. The roles of W and Mo played in increasing corrosion resistance of the steels were different. W could improve the thermodynamic stability of the steel substrate, while Mo could promote the formation of protective rust. Interaction between W, Mo and O2 concentration greatly influenced wet-dry acid corrosion of low-alloy steels. W addition was more effective for depressing charge transfer process at the rust/substrate interface and presented higher enhanced effect on increasing corrosion resistance than Mo under O2 concentration of 1%. Mo was more effective on increasing rust compactness and showed higher enhanced effect on increasing corrosion resistance than W under O2 concentration of 5%.

Inhibitive effect of collagen on the acid corrosion of mild steel in 0.5 M H2SO4 solution was studied by electrochemical impedance spectroscopy and electrochemical frequency modulation. Collagen effectively inhibited the corrosion of mild steel with efficiency ranges from 88.9 to 96.5 % for collagen concentrations from 20 to 80 ppm. Adsorption isotherm study was performed using weight loss measurements where Langmuir and El-Awady models were applied on data to investigate the mode of adsorption. Corrosion inhibition was also tested at different temperatures to measure the thermodynamic parameters; ΔG°, ΔH°, ΔS° and E a. Inhibition is suggested to occur due to adsorption phenomenon and data obey the El-Awady model. Thermodynamic study reveals that adsorption is endothermic–physical process driven by entropic factors.

The corrosion inhibition of mild steel in 0.5 M sulphuric acid by aqueous and acid extracts of leaves of Morinda tinctoria was studied using weight loss, colorimetric and electrochemical techniques. Results obtained indicate that both the extracts are effective in sulphuric acid medium and the efficiency decreases with increase in temperature. Added halide additives improve the efficiency of the inhibitor. From the thermodynamic, spectral, and surface analyses, the nature of adsorption has been found out.

The corrosion inhibitive and adsorption behaviors of Hydroclathrus clathratus on mild steel in 1 M HCl and 1 M H2SO4 solutions at 303, 313 and 323 K were investigated by weight loss, electrochemical, and surface analysis techniques. The results show that H. clathratus acts as an inhibitor of corrosion of mild steel in acid media. The inhibition efficiency was found to increase with increase in inhibitor concentration but to decrease with rise in temperature, suggestive of physical adsorption. The adsorption of the inhibitor onto the mild steel surface was found to follow the Temkin adsorption isotherm. The inhibition mechanism was further corroborated by the results obtained from electrochemical methods. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses supported the inhibitive action of the alga against acid corrosion of mild steel.

Chemicals used presently for corrosion inhibitors in Industries are highly toxic to both human beings and environment. These inhibitors may cause the damage to organ system viz., kidneys or liver, or to disturb a biochemical process of an enzyme system at some site in the body. For papaya seed, a vegetable waste is found to act as a very good green inhibitor, in preventing acid corrosion of low-carbon construction steel. The study was made in 0.5 to 3 N H2SO4 with the variation of concentration. An increase in inhibitor concentration decreases the rate of degradation. But there is an optimum concentration at which the inhibitor effect is maximum, beyond that the corrosion rate again increases. The adsorption study shows that the mechanism of corrosion inhibitor is due to physical adsorption, following Temkin adsorption isotherms. Electrochemical impedance spectroscopy study showed that the corrosion inhibition by the papaya seed is due to an increase in polarization resistance and impedance at metal-solution interface.

[Umoren, Saviour A.; Li, Ying; Wang, Fuhui H.] Chinese Acad Sci, Inst Met Res, State Key Lab Corros & Protect, Shenyang 110016, Peoples R China. [Umoren, Saviour A.] Univ Uyo, Fac Sci, Dept Chem, Uyo, Niger.;Li, Y (reprint author), Chinese Acad Sci, Inst Met Res, State Key Lab Corros & Protect, 62 Wencui Rd, Shenyang 110016, Peoples R China;liying@imr.ac.cn

The worldwide shift towards performance-based standards for concrete demands the advent of performance tests that combine more than one damage mechanism. Such tests can be more reliable in evaluating emerging concrete types such as self-consolidating concrete (SCC). Several applications of SCC involve its exposure to both freezing–thawing cycles and chemical attack, particularly to sulphate-rich media. This study aims at investigating the durability of SCC to sulphate attack coupled with frost action. Potential performance risks of SCC under this dual exposure were identified in terms of various mixture design parameters. Deterioration in physico-mechanical parameters was related to thermal, mineralogical and microscopy analyses, which demonstrated the complex mutual effects of sulphate attack and frost action on SCC specimens. It is shown that SCC mixtures that perform well under the classical ASTM C 1012 test can fail under coupled exposure to freezing–thawing cycles and sulphate attack.

Potentiodynamic polarization was used to investigate the effect of acrolein (formed from propargyl alcohol via acid-induced isomerization) on the electrode processes at Armco iron in hydrochloric and sulfuric acid solutions. In solutions of mineral acids, acrolein is ineffective and inferior to propargyl alcohol in the inhibition of iron corrosion. It was found that acrolein can be cathodically reduced during the corrosion process, whereas the isomerization of propargyl alcohol into acrolein should reduce the protective effect of the inhibitor.

The dependence of the inhibitive effects of new 2-thioquinazolin-4-one derivatives on the corrosivity and pH of the medium was studied. The test compounds were found to effectively inhibit the acid corrosion of steel 20; when combined with (NH4)2MoO4, 2-thioquinazolin-4-one derivatives inhibit both the cathodic and anodic processes of electrochemical corrosion in neutral (0.3 to 0.6% NaCl) and alkaline media (0.1 M NaOH). In 3% NaCl, the test compounds stimulated corrosion.

A procedure was developed for preparing acetylenic esters of bicyclo[2.2.1]hept-5-ene-2-carboxylic acid. The structures of the compounds were confirmed by IR and 1H NMR spectroscopy. The Kovats indices of the compounds were determined, and their boiling points were estimated by gas-liquid chromatography. The protective properties of the esters against acid corrosion of steel were studied.

The inhibiting effect of N-phenacylpyridinium bromides with the amide group in the pyridine ring on corrosion of carbon steel in 3 M sulfuric acid is studied. A relationship between the nature of substituents at the amide group and the corrosion-protective properties of the compounds studied is revealed. Compounds demonstrating high protection efficiency in acid solutions at elevated temperatures are found.

Inhibiting effect on acid corrosion of steel 45 and biocidal activity with respect to sulfate-reducing bacteria are studied for a series of N-aryl-N-(6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[4,3-a]azepin-3-ylmethyl)amines.

Literature data on acetylene compounds as inhibitors of acid corrosion of iron were reviewed. Inhibition mechanism–structure correlations were proposed for classification of acetylene compounds.

Corrosion kinetics of low-carbon steel in hydrochloric acid was studied at various concentrations of mimosa tannin inhibitor. This system was subjected to impedance spectroscopy and quasi steady-state polarization. The inhibition efficiency, η was derived from the corrosion current, icorr and charge transfer resistance, Rct data. The fractional surface coverage as a function of the inhibitor concentration was calculated from the rate of hydrogen evolution reaction (h.e.r.) at constant cathodic potential. Based on the theoretical model and the observed experimental relationship between the ratio of the corrosion current densities in the uninhibited and the inhibited systems and the surface coverage, the relative influences of the geometric blocking action and the energy effect of the inhibitor on the corrosion process were estimated. Fitting of the nonlinear model to the experimental data was carried out by the Levnberg–Marquardt nonlinear fit method implemented into the programming system Mathematica®. Restructuring of the adsorbed layer and change in the orientation of adsorbed inhibitor molecules upon the increase of surface coverage was assumed on the basis of the experimentally observed functional relationship of the double layer capacitance and the surface coverage. The results were explained with respect to the molecular properties of the inhibitor – geometry and size of the molecule, electronic orbital structure and dipole moment.

The effect of traditional inhibitors of acid corrosion (urotropine, benzotriazole, and thiocarbamide) on the corrosion-electrochemical behavior of an iron plate with a tangential thermal gradient in a sulfate-containing acid solution is examined. The inhibitors are shown to significantly weaken the thermogalvanic (TG) corrosion intensity, reducing the TG currents and total weight losses of iron in the thermoelectric zone by factors of 1.3 to 2.0 and 1.1 to 1.4 times, respectively.

We showed that benzazoles are inhibitors of acid corrosion in ozonized solutions of 5% and 20% H2SO4. Benzazoles are oxidized under the action of ozone and decrease its concentration and influence on steel: benzotriazole does so more than benzimidazole. An increase in the of temperature of ozonized solutions of 5% and 20% H2SO4 to 60°C and 40°C, respectively, significantly lowers the inhibiting action of benzotriazole; the inhibiting action of benzimidazole drops with increase in temperature to 40°C and 20°C, respectively.

Potentiostatic and gravimetric methods were used to reveal that the inhibition effect of acetylenic inhibitors (namely propargyl alcohol and propargyl chloride) on the electrode processes of iron and steel corrosion in hydrochloric and sulfuric acids grows with time and temperature, owing to the formation of a polymeric film on the metal surface. In sulfuric acid, propargyl alcohol is easily hydrogenated to give removable reduction products, which lowers its protection effect on steel corrosion.

The structural effect of substituted pyridinium and quinolinium cations on the inhibition of acid corrosion was studied. It was shown to be advisable to apply the HSAB principle with taking in consideration the electronic parameters of these molecules.

Toxicologic data showed that most of the 70 compounds used as inhibitors of metal corrosion are moderately and slightly hazardous (GOST (State Standard) 12.1.007-76 SSBT), and only TsGA, NDA, MSDA-11, and MEA (inhibitors of atmospheric corrosion) and KPI-19 (acid corrosion inhibitor) are highly toxic. For polymethylene amines, azoles, and amino alcohols, a specific dependence of the organotropic effect on the structure was revealed. Corrosion inhibitors can penetrate inside an organism across intact skin to cause both general and local toxic effects. When in toxic doses and concentrations, the inhibitors are characterized by a polytropic action. Some of them have remote after-effects (gonado- and embryotropic, teratogenic, and allergenic) and TAL-3 is carcinogenic. Working conditions in the production and consumption of inhibitors of metal corrosion can be optimized by meeting hygienic, medical, and prophylactic requirements and those on sanitary engineering.

The authors express their gratitude to the Comunidad Auto´noma de Madrid (C226/90) for financial support.

We present experimentally established quantitative regularities of the influence of chemical composition of ortho-substituted pyridines on their anticorrosion activity in sulfuric-acid media.

In continuation of the previous investigations [1, 2] devoted to combined inhibitors of acid corrosion of iron, the protective effects of mixtures of halides with some organic compounds and the mutual influence of their components were determined. Variations of the relevant parameters with the concentration were also studied.

Kinetic features of thermal cyclization of 2-methyl-6-(cyclopent-2-enyl)aniline hydrochloride at 200-220°C were studied. The cyclization product shows a high performance as acid corrosion inhibitor.

Condensation of m-phenoxybenzaldehyde with aromatic amines and hydrazines gave the corresponding Schiff bases and m-phenoxybenzaldehyde arylhydrazones. The products are promising as biologically active substances, polyfunctional additives to rubber compounds, and inhibitors of acid corrosion.

The behaviour of some 3-methyl-l-butyne halo-derivatives towards Armco iron corrosion in 0.5m H2SO4 was examined by the analysis of dissolved iron and electrochemical methods. Their inhibitive performance was determined in relation to the introduced halogen atom with respect to the duration of the tests and temperature. At the same time, these effects were compared to those of 1-octyn-3-ol. In general, the results of the electrochemical methods were found to be in good agreement with those of solution analysis. The possibility of obtaining reliable corrosion data from electrochemical impedance spectroscopy measurements by simply applying the Stern-Geary equation is discussed.

A new inhibitor for steel protection in sulfuric acid solutions, 2'4'6-tribromo-m-phenylenediamine'was studied.

In the 1950s, Ta-7.5%W and the Ta-2.5%W were the only tantalum alloys of commercial significance. An intensive alloy development effort occurred between 1958 and 1968 in response to Air Force and Navy aerospace needs for high-temperature, oxidation-resistant alloys for rocket and air-breathing engines and airframe applications. Compatibility with oxidation-resistant coatings, high-temperature short-time strength, fabricability and weldability were of prime importance. These programs led to the development of Ta-10w%W, Ta-30w%Nb-7.5w%V, T-111(Ta-8w%W-2w%Hf), and T-222(Ta-10w%W-2.5w%Hf-O.Olw%C). T-111, with its demonstrated compatibility with liquid alkali metals, and combination of strength, fabricability and weldability, was selected by NASA as the baseline reference alloy for space nuclear power systems studies. Significant quantities of T- 111 and T-222 were produced in the 1960s. Today, however, production is limited to unalloyed tantalum and the tantalum-tungsten binaries because of the demand of the chemical industry for materials with outstanding acid corrosion resistance. To again produce T-11 and T-222 on a commercial basis will require relearning by the refractory metal alloy producers. The current lack of experience in the refractory metal industry with these high temperature alloys will necessitate recovery of the expertise needed for the United States to effectively compete in this technology arena.

In anesthetized bullfrogs, rabbits and a dog the effect of peptic and tryptic digestion of the hind legs on blood pH, CO2, O2, Cl and N.P.N. was observed. No constant significant change was found and the conclusion is drawn that Calude Bernard’s phenomenon can be explained as slow acid corrosion and subsequent digestion of devitalized tissues. The results confirm the necessity of assuming an additional factor (devitalization) of tissues in the occurrence of gastroduodenal ulcer. Alternation of peptic and trypic digestion greatly increased the rate of digestion.

Inhibitory efficacy has been determined by the method of the weight losses of steel in acid with native lignin, hydrolysis lignin, ammoniated native lignin, chlorinated hydrolysis lignin, and ammoniated hydrolysis lignin, and without these additives. It has been established that the efficacy of lignin and its modifications as inhibitors of acid corrosion increases with a rise in the number of carboxy groups in the macromolecule, and therefore the ammoniated hydrolysis lignin is the most effective.

The effect of certain acid corrosion inhibitors on the ductility of steel 45 was studied on wire specimens stressed in torsion in an aqueous sulfuric acid solution. It was shown that the best protection against hydrogen embrittlement of steel is offered by inhibitors AGMIB and APB.