Akram Alfantazi

Corrosion Properties of Pulse-Plated Zinc-Nickel Alloy Coatings

Abstract Corrosion properties of pulse-plated Zn-Ni alloy coating on a steel substrate were investigated using the neutral salt-spray test (ASTM B 117-81) and the potentiodynamic polarization techn...

Mechanisms of Corrosion and Electrochemical Significance of Metallurgy and Environment with Corrosion of Iron and Steel in Bicarbonate and Carbonate Solutions—A Review

This paper presents an electrochemical review on the corrosion behavior of iron and steel in bicarbonate and carbonate solutions. The mechanisms of dissolution and passivation are at first consolid...

Corrosion of Titanium and Its Alloys in Sulfuric Acid in the Presence of Chlorides

Titanium alloys (ASTM Grades 1, 2, 7, 12, and 18) are employed as the liner and internal components of autoclaves during the high-pressure acid leaching (HPAL) of nickel laterite ores. This paper summarizes the corrosion behavior of these alloys in sulfuric acid and the effect of the addition of chlorides (NaCl). New thermodynamic Eh–pH diagrams for the Ti–H2O, Ti-SO4–H2O, and Ti–Cl–H2O systems are presented. Micrographs are also presented and the corrosion morphology is discussed. Long-term immersion tests were carried out to determine corrosion rates. Electrochemical techniques were used to provide insight into the corrosion chemistry. The shortcomings of accelerated corrosion testing of Ti alloys are addressed. Pd enrichment on the surface of Ti-18 was confirmed by a combination of open-circuit potential measurements and chronoamperometric measurements.

An investigation on the effects of orthophenylene diamine and sodium lignin sulfonate on zinc electrowinning from industrial electrolyte

Abstract In this work, we investigated the effects of orthophenylene diamine (OPD) and sodium lignin sulfonate (at a range of 3–10 ppm) in industrial zinc sulfate electrolyte on the current efficiency, the energy consumption of zinc electrowinning, and the physical characteristics of zinc deposits. The electrowinning experiments were conducted using a laboratory-scale apparatus, at a plating time of 80 min, a current density of 500 A m −2 , and a temperature of 38 °C. Industrial zinc sulfate electrolyte having zinc and H 2 SO 4 concentrations of 62 and 170 g L −1 , respectively, was employed. Scanning electron microscopy (SEM) was used to characterize the zinc deposits with respect to surface morphology. The results clearly showed that OPD had a very negative (catastrophic) effect on the current efficiency and, consequently, the power consumption of zinc electrowinning. Current efficiency dropped from about 90% at no addition to less than 60% at only 3 ppm addition level. On the other hand, the addition of up to 10 ppm sodium lignin sulfonate had no negative impact on the zinc electrowinning process, nor on the quality of the zinc deposits.

Role of Thiosulfate in the Corrosion of Steels: A Review

Thiosulfate salts have been known to be dangerous corrosion promoters for over 30 y, when present under typical service conditions. This paper reviews the role of thiosulfate anion in causing localized corrosion and/or stress corrosion cracking of steels. Electrochemical and mechanical aspects associated with the pitting and stress corrosion cracking of steels in thiosulfate-containing environments are thoroughly discussed and reviewed. In particular, results from the research studies relevant to pulp and paper, oil and gas, and nuclear industries, where thiosulfate ion is known to be present advertently or inadvertently, have been analyzed.

Physicochemical Properties of Alkaline Aqueous Sodium Metaborate Solutions

Background: The transition to a hydrogen fuel economy is hindered by the lack of a practical storage method and concerns associated with its safe handling. Chemical hydrides have the potential to address these concerns. Sodium borohydride (sodium tetrahydroborate, NaBH 4 ), is the most attractive chemical hydride for H 2 generation and storage in automotive fuel cell applications, but recycling from sodium metaborate (NaBO 2 ), is difficult and costly. An electrochemical regeneration process could represent an economically feasible and environmentally friendly solution. Method of Approach: We report a study of the properties of concentrated NaBO 2 alkaline aqueous solutions that are necessary to the development of electrochemical recycling methods. The solubility, pH, density, conductivity, and viscosity of aqueous NaBO 2 solutions containing varying weight percentages (1, 2, 3, 5, 7.5, and 10 wt. %) of alkali hydroxides (NaOH, KOH, and LiOH) were evaluated at 25 ° C. The precipitates formed in supersaturated solutions were characterized by X-ray diffraction and scanning electron microscopy. Results: All NaBO 2 physicochemical properties investigated, except solubility, increased with increased hydroxide ion concentration. The solubility of NaBO 2 was enhanced by the addition of KOH to the saturated solution, but decreased when LiOH and NaOH were used. The highest ionic conductivity (198.27 S/m) was obtained from the filtrate of saturated aqueous solutions containing more than 30 wt. % NaBO 2 and 10 wt. % NaOH prior to filtration. At 10 wt. % hydroxide, the viscosity of the NaBO 2 solution was the highest in the case of LiOH (11.38 cP) and lowest for those containing NaOH (6.37 cP). The precipitate was hydrated, NaBO 2 for all hydroxides, but its hydration level was unclear. Conclusions: The use of KOH as the electrolyte was found to be more advantageous for the H 2 storage and generation system based on NaBO 2 solubility and solution half-life. However, the addition of NaOH led to the highest ionic conductivity, and its use seems more suitable for the electroreduction of NaBO 2 . Further investigations on the impact of KOH and NaOH on the electroreduction of NaBO 2 in aqueous media have the potential to enhance the commercial viability of NaBH 4 .

Influence of Cupric, Ferric, and Chloride on the Corrosion of Titanium in Sulfuric Acid Solutions Up to 85°C

Titanium is chosen as the construction material of autoclaves for pressure acid leaching of metal ores. The corrosion behavior of titanium was studied in sulfuric acid solutions with different addi...

The Effects of Chloride Ions on the Electrowinning of Nickel from Sulfate Electrolytes

In this work, the effects of chloride ions on the electrowinning of nickel from sulfate electrolytes has been studied. Specifically, the influence of the chloride ion concentration in the range of 0-1000 mg/L on the current efficiency, and power consumption of electrowinning, surface morphology, and preferred orientation of nickel deposits have been determined. The current efficiency increased while the power consumption decreased in the presence of chloride ions over the concentration range studied, the maximum being 1000 mg/L. X-ray diffraction analysis of the nickel deposits produced from electrolytes with chloride ions indicated the presence of (111), (200), (220), (311), (400), (331), and (222) orientation, with a slight (200) and (220) preferred orientation. By using scanning electron microscopy changes in the surface morphology and appearance of the nickel deposits were also observed as a result of chloride ion additions.

Effect of Oxygen on the Corrosion Behavior of Alloy 625 from 25 to 200 ° C

Electrochemical polarization and impedance experiments were conducted on alloy 625 in ammoniacal solution between 298 and 473 K and at various oxygen partial pressures. Increased oxygen concentrations (as a result of higher temperatures or autoclave oxygen loading) resulted in increased corrosion potentials and corrosion rates. The inversion temperature (onset transpassive corrosion) was found to be ∼ 373 K at P TOTAL > 40 bar. A binary barrier layer/ outer layer film configuration was assumed and it was found that the outer layer dominated the corrosion process as temperatures and pressures were increased such that oxygen diffusion control was rate limiting. An oxygen solubility model for supercritical water oxidation (SCWO) conditions was generated using the Redlich-Kwong-Soave equation of state. Results of the model experimental work confirm many of the observations from SCWO reactors which suggest that corrosion reaches a maximum at temperatures just short of the critical point. Exchange current densities for oxygen reduction and effective diffusion layer thicknesses have also been calculated.

A study of copper electrowinning parameters using a statistically designed methodology

This study employs a factorial experimental design to relate current efficiency with current density (180 and 300 A m−2), copper concentration (25 and 65 g l−1), and temperature (40 and 60 °C). Pure, synthetic electrolyte with a constant acid concentration of 180 g l−1 was used. The designed study produced a linear relationship where the independent variables of current density, copper concentration, temperature and their interactions were found to be statistically significant. It was shown that current efficiency could not solely be used as a predictor of copper cathode quality. The quality of the deposit is difficult to incorporate into a model or relation. It was determined that other measures, such as cathode morphology and crystal structure should be considered. This was done through XRD and SEM analysis.