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The corrosion behavior of microporous chromium plating systems in concentrated aqueous electrolytes was studied to describe the so-called Russian-mud corrosion of microporous chromium plating systems from decorative car parts. Corrosive stressed chromium plating systems from Russia were analyzed with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) to characterize the specific corrosion mechanism. The electrochemical corrosion behavior was evaluated by potentiodynamic polarization curves, zero resistance ammetry and electrochemical impedance spectroscopy (EIS). The obtained results show two different corrosion mechanisms, dissolving of the chromium plating and undercutting of the chromium plating at specific conditions. [ABSTRACT FROM AUTHOR]

The non-ferrous metal industry, such as Cr/Ni/Cu plating, produces acid sludge which is usually neutralized with lime slurry in batch processes, and the resulting waste is dewatered by vacuum filtration or filter-pressing. Dewatered sludge contains calcium sulphate (CaSO 4 ) coming from the neutralization process, as well as transition metals (Cr, Ni and Cu), oil, grease and suspended solids. In this communication, two residual sludges from Cr/Ni/Cu plating have been dried (110 °C) and fired (1100 °C), and both dried (gray coloured) and fired powders (black coloured) have been characterized by DTA-TG, XRD and SEM-EDX techniques. XRD shows only quartz crystallization in dried samples, while NiCr 2 O 4 chromite spinel and NiO periclase crystallize in fired powders, along with CaSO 4 anhydrite and CaSiO 3 wollastonite. The powders have been introduced as ceramic pigments into three different conventional glazes: a) a lead bisilicate (PbO.2SiO 2 ) double fire frit (1000 °C), b) a double fire frit with low lead content (1000 °C), and c) a double fire frit without lead (1050 °C). Glazed samples were characterized by UV-Vis-NIR (diffuse reflectance) and CIEL∗a∗b∗ (color parameters). Dried powders induce glaze defects (pin-holing and crawling), but fired powders did not show these faults exhibiting more intense (higher L ∗ ) and yellowish (higher b ∗ ) black colors than the standard spinel. [ABSTRACT FROM AUTHOR]

ABSTRACT: In this work, chrome‐plated acrylonitrile–butadiene–styrene (ABS) parts containing defects in the deposited metal layer were pickled up to two times in hydrochloric and nitric acid under different immersion times. The influence of pickling on the properties of ABS was evaluated by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy–attenuated total reflection (FTIR–ATR), scanning electron microscopy, atomic force microscopy, and roughness. The pickled parts were again chromed and evaluated by visual inspection and adhesion. The metallic layer was removed and a slight yellowing of the samples surface with the increase of pickling time. There were no significant changes in the thermal behavior of the material. Some of the components of ABS were removed, as evidenced by the reduction of the absorption peaks intensity in FTIR–ATR, by the increase of roughness and presence of pores on the surface. With the increase of the immersion time and the number of pickling, there was the formation of pores with larger sizes and decrease in roughness, making metal–polymer adhesion difficult. Only one pickling, under immersion time of 30 min, was adequate for the removal of the metallic layer, allowing new chrome plating. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46131. [ABSTRACT FROM AUTHOR]

In the present study, WC-CoCr hard composite coatings were deposited on the hydro turbine steels using two different thermal spray techniques such as High Velocity Air Fuel (HVAF) and High Velocity Oxy Fuel (HVOF). The slurry erosion tests were performed with three different jet impingement kinetic energies and at five different impact angles. The influence of impact angle on the erosion wear behavior of the coatings was analyzed using CFD simulation technique. Erosion mechanisms were investigated in detail using SEM and laser scanning confocal microscopy. Among all the WC–CoCr coated samples, the HVAF coating sprayed at highest spray velocity has shown superior erosion resistance compared to the HVOF coatings. It could be attributed to the better adhesion, higher density, enhanced hardness and surface compressive residual stresses coupled with lower oxidation of the coated samples. The erosion wear mechanisms were found to be nearly micro-cutting and plowing with layered material removal at a lower impact angle and a low cycle fatigue linked to repeated impact leading to rounding of the edges and brittle cracking of the WC grains at normal impact conditions. [ABSTRACT FROM AUTHOR]

The CrCN coatings were fabricated onto Si (1 1 1) wafers and SUS304 stainless steel plates using filtered cathodic vacuum arc deposition (FCVAD) technique under different flow ratios of N 2 /C 2 H 2 gas mixture. The morphology, crystalline structure and chemical composition of the coatings were characterized. It was found that the grain size reduce with increasing carbon content, which makes the CrCN coatings refined and smooth. The quasi-one-dimensional carbolite phase was also found in CrN host lattice with C 2 H 2 content ranging from 5% to 20%, and it will be evolved into amorphous carbon and amorphous CN x phases as C 2 H 2 content exceeds 20%. Moreover, we examined the mechanical and tribological properties of the CrCN coatings, and the experimental results confirmed that the friction coefficient of the coatings descend to the lowest value as 0.39 with 30% C 2 H 2 content, due to the graphite (sp 2 C C) phase embed in CrN host lattice; while the chromium carbon (Cr 3 C 2 ) and diamond (sp 3 C C) phases may give rise to the increase of the coating hardness with the highest value at 23.97 GPa under 20% C 2 H 2 content. [ABSTRACT FROM AUTHOR]

Purpose Compression rings are the main sources of frictional losses in internal combustion engines. The present paper aims to present a thermo-mixed hydrodynamic analysis for coated top compression rings. To understand the coating effects, the main tribological parameters are investigated into a ring-cylinder conjunction in a motorbike engine. Furthermore, flow simulations have been carried out on how different worn profiles on the cylinder inner liner affects friction, lubricant film and localized contact deformation of the coated compression rings.Design/methodology/approach In this paper, the basic geometrical dimensions of the top compression ring-cylinder system are obtained from a real motorbike engine. A 2D axisymmetric CFD/FLOTRAN model is created for coated compression rings. Flow simulations are performed by solving the Navier-Stokes and the energy equations. The load capacity of the asperities is also taken into account by Greenwood and Tripp contact model. Realistic boundary conditions are imposed to simulate the in-plane ring motion. The simulation model is validated with analytical and experimental data from the literature. Under thermal considerations, the contribution of worn cylinder profiles in conjunction with different coated compression rings is presented.Findings This research shows that because of thermal effects, the boundary friction is higher at reversals and the viscous friction is lower because of reduced oil viscosity. As regards to the isothermal case, the viscous friction is greater because of a higher lubricant viscosity. In the case of chromium-plated ring, boundary friction was 16 per cent lower than a grey cast iron ring taking into account thermal effects. Regarding the localized contact deformation, the coated compression rings showed lower values under different worn cylinder shapes. In particular, hard wear-resistant (Ni-Cr-Mo) coating showed the slighter local deformation. Therefore, the worn cylinder profiles promote boundary/mixed lubrication regime, whereas the lobed profile of cylinder inner liner becomes more wavy.Originality/value The solution of the thermo-mixed lubrication model, concerning the piston ring and worn cylinder tribo pair by taking into account the coating of the top compression ring. [ABSTRACT FROM AUTHOR]

In this work, olive stone (OS) was utilized to investigate its capacity as biosorbent for methylene blue (MB) and Cr(III), which are usually present in textile industry effluents. Equilibrium and kinetic experiments were performed in batch experiments. The biosorption process followed pseudo-second-order kinetics. The equilibrium data were fitted with several models, but Langmuir and Sips models best reproduced the experimental results. Maximum biosorption capacities were 3.296 mg/g (0.0116 mmol/g) and 4.990 mg/g (0.0960 mmol/g) for MB and Cr(III), respectively. Several operation variables, such as biosorbent mass, flow rate, and initial concentration on the removal of dye and metal, were evaluated in column system. The removal efficiency improved as OS mass increased and decreased when flow rate and initial concentration increased. Also, MB uptake was substantially decreased by increasing the initial concentration of Cr(III), ranging from 6.09 to 2.75 mg/g. These results show that the presence of Cr(III) significantly modifies the biosorption capacity of MB by the OS. These results suggest that OS is a potential low-cost food industry waste for textile industry wastewater treatment. [ABSTRACT FROM PUBLISHER]

The use of plastic in vehicle development has increased. In particular, a design trend has resulted in chromiumplated plastics being used in exterior panels. Recently, as the appearance has become more important in design, the plastic radiator grille has become larger, to where it can become the primary member when a front collision happens. The radiator grille should be designed with considerations of the geometric structure, such as delamination, and material characteristics, when plastics are plated with chromium. The enlarged grille has to pass regulations like FMVSS Part 581. Although the material property of plastic has been studied before, what seems to be lacking is study on the crashworthiness of plastic radiator grilles that are plated using chromium. In this paper, in order to evaluate the crashworthiness, tensile test and front collision analysis using finite element method are performed. Tensile test is conducted with 4 types of materials, and then material properties of chromium-plated plastics are obtained. Meanwhile radiator grille's crashworthiness is evaluated using finite element analysis method. Analysis result is evaluated according to failure criterion. Through this study, method of the assessment of plastic radiator grille's crashworthiness considered material properties of chromium plated plastics is proposed, and it can be predicted the delamination and the failure point of radiator grille at the design step. [ABSTRACT FROM AUTHOR]

The relevance of studying product quality control as based on optimization of process input values parameters is shown. The paper explores the tolerance synthesis method of technological process input parameters based on regression dependences. Electrolytic chromium plating process simulation has been performed enabling to optimize input parameter tolerances and upgrade process equipment. As a result of the modernization the galvanic bathtubs were outfitted for control parameters of the electrolyte, heating of the electrolyte. The modernization of electrolytic chromium plating process allowed finding of values of input parameters being within the required limits and providing for the quality of the products. [ABSTRACT FROM AUTHOR]

The effect of addition of molybdenum in Fe Cr Mn based alloy on the chromium deposition and poisoning of LSM cathodes is investigated at 800 °C by electrochemical impedance spectroscopy and microstructure analysis. The Fe Cr Mn Mo ferrite stainless steel metallic interconnect shows much less Cr deposition and poisoning on the LSM cathodes as compared with the Fe Cr Mn alloy. The addition of Mo into the alloy suppressed Cr evaporation from interconnects, decreased the degradation of cathode performance caused by Cr. According to SEM results, MoO 3 and MnMoO 4 is observed at the depositional area. The segregated MnO from LSM cathode can act as a nuclei agent, and react with vaporized Mo to form Mo-contained oxide particles, which will not inhibit the oxygen reduction reactions in the three phase boundary (TPB). As a result, suitable addition of Mo into the interconnect alloy can effectively alleviate the Cr poisoning of the LSM cathode. [ABSTRACT FROM AUTHOR]

Nanochromium coatings were deposited on 316L stainless steel bipolar plates of a proton-exchange membrane fuel cell (PEMFC) by a direct current magnetron sputtering technique. The effect of substrate temperature on the corrosion resistance of nanochromium coatings was investigated. The corrosion performance of the bare and chromium-coated steel in a simulated environment of PEMFC (0.5 M H2SO4 + 2 ppm F−) was studied using electrochemical impedance spectroscopy, polarisation, and open circuit potential measurements. The results showed that the corrosion rates of two nanochromium coatings deposited at 300°C and 500°C were lower than those of uncoated steel by more than one order of magnitude. Electrochemical impedance spectra of both nanochromium coatings exhibited distinct characteristics in corrosive solution. The nanochromium coating deposited at 500°C showed superior stability in the corrosive solution. [ABSTRACT FROM AUTHOR]

Heat treatment is widely used for high reliability fastening components such as buckles and brackets. The current study focuses on mass production of safety components which are fineblanked from sheet metal, austempered and chromium electroplated. Electroplating together with stamping defects may lead to unexpected brittle failure of the component. It is widely known that during austenitisation, decarburisation could avoid brittle failure and, therefore, slight decarburisation is recommended. There is little information how much mass production is influenced by decarburisation and where the limits are. The current study has two goals. The first one focuses on the extent of decarburisation effect on the part properties, and the second aims to find the optimum furnace setting for the product type used in the study. Also, it is necessary to choose a reliable decarburisation control method for austempered components. The effect on material grades was analyzed by using three steel alloys with carbon content of 0.37 wt.%, 0.47 wt.% and 0.62 wt.%. The specimens were austempered to hardness 45 - 51 HRC under endothermic protective atmosphere. To gain different decarburisation levels, two gas set-ups were used. Infrared gas analyzer was used to measure CO and CO2 content in the furnace gas. Three characteristics of the specimens were evaluated: hardness, rupture strength and brittleness. The depth of the decarburisation was determined by three different approaches according to standard EN ISO 3887. Based on the results, the spectrographic method is the most reliable for determining the depth of decarburisation. This study reveals that higher surface decarburisation has a positive effect on the ductility and no effect on the rupture strength of the component. The material with carbon content of 0.62 wt.% is the most sensitive to decarburisation. During mass production, the inaccuracy of hardness measuring raises which results in the inaccuracy of salt bath temperature regulation. For the used thermal cycle, the furnace gas carbon potential 0.30 - 0.40 has to be used to ensure expected performance of fastening products. [ABSTRACT FROM AUTHOR]

This work deals with the development and optimization of the sample pretreatment and consequent electrophoretic analysis of twomodern plating baths containing chromium(III) and either citric acid or oxalic acid. Some model mixtures containing known amounts of components of industrial baths have been prepared to simulate simplified bath matrices. Prior to analysis, a sample pretreatment consisting of the addition of some agents that could release acid from the stable chromium complex was tested. Determination of organic anions was accomplished by indirect UV detection. The best results were achieved by precipitation of chromium(III) hydroxide. The content of oxalate and citrate in real samples was calculated as 96.5% (SD 2.3%) and 97.3% (SD 0.8%), respectively, of the declared amount. Very good robustness of the method and satisfactory repeatability of migration time and peak area were obtained. This simple inexpensive method is suitable for routine determination of citric and oxalic acid in chromium(III)-based plating baths. [ABSTRACT FROM AUTHOR]

A nanocomposite composed of metal-phosphates and chromium oxide was prepared from a Cr(III)-containing electroplating sludge (CES) by a facile three-step (extraction-precipitation-calcination) process. Optimal process parameters were determined, and the structure of the metal-phosphate/chromium oxide nanocomposite (MPCON) was investigated by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show that the optimal extraction pH is 2.0. The MPCON presents a polyhedral morphology with average particle size of around 100 nm. The components of MPCON vary from AlPO4/Cr2O3 to Mg3(PO4)2/AlPO4/Cr2O3 at different solution pH during precipitation. Meanwhile, the optical performance of the nanocomposite as a pigment is discussed. The reflectance of MPCON-6.5 in the near-infrared range is around 56%, making it a strong prospect to be used as a functional pigment in energy-efficient buildings. This study proposes a novel recycling process for the conversion of CES into high-value products, which is beneficial for the treatment of waste. [ABSTRACT FROM AUTHOR]

This article explains the application of the Reliability-Centered Maintenance (RCM) approach to developing maintenance planning in Hard Chrome Plating plants. The key to the RCM purpose is an effectual maintenance planning of plant components inherent in their reliability value. Also, this research aims to reduce machine downtime maintenance that stems from machine breakdown and to select preventive maintenance activities based on the engineering reliability for the machine parts. The first step of the research involves setting a priority for critical parts of the Hard Chrome Plating machine. After that, we analyze the damage and risk level data by using Failure Mode and Effects Analysis (FMEA) for calculating a suitable reliability parameter. The final step is to select the preventive maintenance task. As a result of this research, the failure rate of the plant can be reduced 9.22% and the machine availability rate of the plant is increased to 80.34% accordingly. Following this theme, a maintenance plan for the plant is conducted with respect to this RCM concept. Application of the RCM approach revealed that the key time between plant equipment failures and the likelihood of abrupt equipment failures are reduced. [ABSTRACT FROM AUTHOR]

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Voltammetric and impedance techniques are used to determine the protective ability of chromium coatings deposited on a steel substrate from sulfate and methanesulfonate electrolytes based on trivalent chromium. It is found that chromium deposits obtained from methanesulfonate electrolyte have lower porosity and higher protective ability as compared with deposits from sulfate electrolyte. It is shown that, when the thickness of chromium coatings reaches 15 μm, there are no through pores in deposits for both electrolytes and, thus, the maximum degree of protection of the steel support is achieved in an aggressive medium. An equivalent circuit correctly modeling the corrosion-electrochemical behavior of the studied system is proposed on the basis of data of electrochemical impedance spectroscopy, and the values of its parameters are calculated. [ABSTRACT FROM AUTHOR]

A novel modular tank layout, which flexibly adapts to various electroplating processes, is introduced and its feasibility has been studied by a three-dimensional simulation model. The new layout uses floor space and process volume more effectively and brings necessary novelty to the electroplating industry which partially suffers from outdated process equipment and low competitiveness. Trivalent chromium plating has been chosen as a test process in the simulation model since replacing hexavalent chromium is an important issue in the industry. The simulation model has been verified by conducting an extensive series of experimental coating thickness measurements and supplementing the model with these results. The results of the simulations support the feasibility of the new tank layout and show that it is possible to obtain good coating thickness uniformity when running separate coating processes simultaneously in one tank with different plating currents and surface areas of the objects to be plated. [ABSTRACT FROM AUTHOR]

To catalyze Cr(III)/Cr(II) redox couple, Pb was used as candidate catalysts. Pb has a remarkable behavior on reduction and oxidation of chromium couple to enhance the performance of Fe-Cr redox flow cell. In the present investigation catalyzed carbon felt substrates were used as electrodes on negative side which were electrochemically plated/ loaded with Pb from 0.05g to 1.2g. The cell comprising 0.8 g Pb loaded felt has shown 100% Chromium reduction efficiency, 98% coulombic efficiency and zero hydrogen gassing at 32°C for 15 cycles of charge and discharge. 5liters of 1.3N FeCl2 in 2N HCl as catholyte, 1.3N CrCl3 in 2N HCl as anolyte containing 0.05N BiCl3 as additive were used as electrolytes. The cell operated with Nafion-117 PFSA membrane. 100 cm2 GFA grade carbon felts with 3mm thickness were utilized as electrodes at a current density of 50 mA/cm2. [ABSTRACT FROM AUTHOR]

The article focuses on the biological monitoring of metallic elements in the electroplating industry. It evaluates the risk of exposure to hexavalent chromium by the workers in the chromium plating industry. It also discusses innovative techniques used to measure the exposure to hexavalent chromium including exhaled breath condensate (EBC), which assess the absorbed dose at the target organ level, its pneumotoxic effects and the pulmonary reduction kinetics of the metal.

Abstract: Formation of multi-layer coating by plasma nitriding and hard chromium electroplating on the surface of H11 hot work tool steel was investigated. Specimens were coated via a triple process containing plasma nitriding, hard chromium electroplating and plasma nitriding. Surface composition has been studied by X-ray diffraction analysis. The surface morphology and elemental analysis was examined by using scanning electron microscopy. Wear tests were conducted by the use of pin-on-disk method, a cemented tungsten carbide pin and 1000 gF load. Polarization corrosion tests were carried out in distilled water solution containing 3% NaCl. The improvement in hardness distribution after third step is discussed in considering the forward and backward diffusion of nitrogen in the chromium interlayer. Also, the formed phases in the hybrid coating were determined to be CrN + Cr2N + Cr + Fe2–3N + Fe4N. Wear results showed that although the multi-layer coated specimens have higher wear resistance in comparison with the reference specimen, their wear resistance is less than that of two and one layer coated specimens due to micro-ploughing and removal of hard surface nitrides from the surface. By increasing the third step time and temperature, the wear resistance of specimens increases due to higher diffusion of nitrogen in the chromium layer. But polarization results showed that triple coated specimens have the lowest corrosion rate. [Copyright &y& Elsevier]

Abstract: Chromium plating used for functional purposes provides an extremely hard, wear and corrosion resistant layer by means of electrolytic deposition. Typical layer thicknesses range between 2.5 and 500μm. Chromium electroplating baths contain high concentrations of Cr(VI) with chromium trioxide (CrO3) as the chromium source. When because of technical or economic reasons a bath gets exhausted, a waste containing mainly chromium as dichromate as well as other heavy metals is generated. Chromium may then be purified for use in other industrial processes with different requirements. In this work, a sustainable system for using galvanic wastes as reagents in the leather tanning industry, thus reducing quantity of wastes to be treated, is presented. Metal cations present in the chromium exhausted bath were precipitated with NaOH. Then, the solution containing mainly soluble Cr(VI) was separated. By means of sodium sulphite in acidic conditions, Cr(VI) was reduced to Cr(III) as chromium (III) sulphate. From chromium (III) sulphate a basic Cr(III) sulphate may be obtained, which is one of most used compounds in the tanning industry. Cr(III) concentration in the final solution allows its reuse without concentration, but with a slight dilution. [Copyright &y& Elsevier]

Manganese cobalt oxides are promising coating materials for reducing chromium volatilization, and thus the associated cathode poisoning, from interconnect alloys in solid oxide fuel cells ( SOFCs). Interaction between this coating and the oxide scale formed on the alloy during fuel cell operation can lead to changes in the coating composition and thus its performance. In this study, the properties of manganese cobalt spinel oxides and the reaction between manganese cobalt spinel oxides and chromia were investigated. The reaction product consists of two layers: a layer in contact with chromia that grows by the diffusion of cobalt and manganese from (Mn,Co)3O4 toward the chromia and an intermediate layer that grows by the diffusion of chromium through the reaction layer. The effect of dopants on the coating performance was also investigated. With the addition of iron or titanium, the rate of reaction between the spinel coating and the chromia scale can be decreased significantly, which would reduce the risk of scale spallation and provide an increase in the lifetime of the interconnect and thus the fuel cell. [ABSTRACT FROM AUTHOR]

Abstract: The transport properties of a cation-exchange membrane in the presence of nickel sulphate solutions were investigated by means of chronopotentiometry. The interest of this study relies on the application to the treatment of chromium plating rinse baths. The presence of chromic acid in the solutions and the initial concentration of nickel sulphate affect significantly the shape of the chronopotentiograms. The different shape of chronopotentiograms as well as the values of different parameters is thereby justified by the calculation of the speciation diagrams of Ni(II). Parameters like the limiting current density, resistance of the ohmic region, plateau length, and nickel transport numbers through the cation-exchange membrane were calculated from the chronopotentiometric and the current–voltage curves. The obtained results show an important competence between Ni2+ and H+ ions, with increases of the nickel transport numbers when the [Ni2+]/[H+] ratio corresponding to the initial equilibrium exceeds the unity. The increase in the Ni2+ concentration brings about a facilitated arising of electroconvection, which promotes overlimiting currents and additional mixing at the membrane surface. [Copyright &y& Elsevier]

Purpose: Real electroplating effluents contain multiple metals. An important point related with the feasibility of the bioremediation process is linked with the strategy to recover selectively metals. In this work, a multimetal solution, obtained after microwave acid digestion of the ashes resulted from the incineration of Saccharomyces cerevisiae contaminated biomass, was used to recover selectively chromium, copper, nickel, and zinc. Results: The acid solution contained 3.8, 0.4, 2.8, and 0.2 g/L of chromium(III), copper, nickel, and zinc, respectively. The strategy developed consisted of recovering copper (97.6%), as a metal, by electrolyzing the solution at a controlled potential. Then, the simultaneous alkalinization of the solution (pH 14), addition of HO, and heating of the solution led to a complete oxidation of chromium and nickel recovery (87.9% as a precipitate of nickel hydroxide). After adjusting the pH of the remaining solution at pH 10, selective recovery of zinc (82.7% as zinc hydroxide) and chromium (95.4% as a solution of cromate) was achieved. Conclusion: The approach, used in the present work, allowed a selective and efficient recovery of chromium, copper, nickel, and zinc from an acid solution using a combined electrochemical and chemical process. The strategy proposed can be used for the selective recovery of metals present in an acid digestion solution, which resulted from the incineration of ashes of biomass used in the treatment of heavy metals rich industrial effluents. [ABSTRACT FROM AUTHOR]

This laboratory-scale study explored the use of rice husk ash (RHA) as an admixture to stabilize and solidify the waste sludge from a chrome-tanning process. Various ratios of RHA and tannery sludge were used, ranging from 0.25 to 1.0 by weight of the cement content, resulting in an experimental matrix of 16 runs. It was observed that although the compressive strength of solidified sludge improved at longer curing times, the increase was moderate after 7 days of curing. In addition, higher RHA and/or sludge ratios progressively reduced the strength of the samples. On the other hand, curing time had a positive effect on chromium leachability since the leaching concentration decreased considerably with an increase in curing time, up to 28 days. Furthermore, both the RHA and/or sludge content affected leachability, producing acceptable results, from a Thai regulatory perspective, at ratios of 0.50 or lower. Finally, the solidified sludge can be disposed of in a secure landfill and/or used as a construction material in a number of applications. [ABSTRACT FROM AUTHOR]