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D. Thirumalaikumarasamy ¹, K. Shanmugam ¹, V. Balasubramanian ¹, S. Sree Sabari ¹

Affiliations
1 Department of Manufacturing Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamil Nadu, IN

Abstract

An investigation was carried out to quantify and characterize the corrosion behaviour of AZ31B magnesium alloy. The specimens were underwent immersion, salt spray, pitting and galvanic corrosion tests in order to quantify and characterize the corrosion rates of the AZ31B specimens with the influence of different pH values, chloride ion concentration and the corrosion time. An attempt was also made to develop an empirical relationship to predict the corrosion rate of AZ31B magnesium alloy. Three factors, five level, central composite rotatable design matrix was used to minimize the number of experimental conditions. Response surface methodology was used to develop the relationship. The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95% confidence level. The results show that the corrosion rate was higher in salt spray corrosion tests than the immersion, pitting and galvanic corrosion tests.

Keywords

AZ31B Magnesium Alloy, Response Surface Methodology, Corrosion Rate.

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D. Thirumalaikumarasamy ¹, K. Shanmugam ¹, V. Balasubramanian ¹

Affiliations
1 Department of Manufacturing Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamil Nadu, IN

Abstract

Plasma sprayed ceramic coatings are successfully used in many industrial applications, where high wear and corrosion resistance with thermal insulation are required. The corrosion degradation of a uncoated and atmospheric plasma sprayed alumina (APS) coatings on AZ31B magnesium alloy was investigated using immersion corrosion test in NaCl solutions of different chloride ion concentrations viz., 0.01 M, 0.2 M, 0.6M and 1M. The corroded surface was characterized by an optical microscope and X-ray diffraction. The results showed that the corrosion deterioration of uncoated and coated samples were significantly influenced by chloride ion concentration. The uncoated magnesium and alumina coatings was found to offer a superior corrosion resistance in lower chloride ion concentration NaCl solutions (0.01M and 0.2MNaCl). On the other hand the coatings and Mg alloy substrate were found to be highly susceptible to localized damage, and could not provide an effective corrosion protection in solutions containing higher chloride concentrations (0.6M and 1 M). It was found that the corrosion resistance of the ceramic coatings and base metal gets deteriorated with the increase in the chloride concentrations.

Keywords

Atmospheric Plasma Spraying, Magnesium Alloy, Chloride Ion Concentration, Corrosion, NaCl.

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D. Thirumalaikumarasamy ¹, K. Shanmugam ¹, V. Balasubramanian ¹

Affiliations
1 Department of Manufacturing Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamil Nadu, IN

Abstract

In this study, an attempt has been made to establish an empirical relationship is developed to predict corrosion rate of the atmospheric plasma sprayed alumina coatings on AZ31B magnesium alloy by incorporating process parameters such as power, stand-off distance and powder feedrate. Statistical tools such as design of experiments, analysis of variance, and regression analysis are used to develop the relationships. The developed empirical relationship can be effectively used to predict the corrosion rate of plasma sprayed alumina coated AZ31B magnesium alloy at the 95% confidence level. Sensitivity analysis was carried out and compared with the relative impact of three process parameters on corrosion rate to verify the measurement errors on the values of the uncertainty in estimated parameters. The results indicate that the input power has the greatest influence on corrosion rate, followed by stand-off distance and powder feedrate.

Keywords

Atmospheric Plasma Spraying, Corrosion Rate, Response Surface Methodology Alumina Coating.

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D. Thirumalaikumarasamy ¹, K. Shanmugam ¹, V. Balasubramanian ¹

Affiliations
1 Dept of Manufacturing Engineering, Annamalai University, Annamalainagar, Chidambaram, Tamil Nadu, IN

Abstract

The comparative evaluation of corrosion behavior of AZ31B magnesium alloy was investigated by conducting immersion and salt spray tests in NaCl solution. The specimens were exposed to immersion and salt spray environments in order to characterize their corrosion rates. In addition, an attempt was made to develop an empirical relationship to predict the corrosion rate of the AZ31B magnesium alloy in immersion tests and salt spray corrosion tests using response surface methodology. The corrosion morphology observation was carried out by scanning electron microscopy. General corrosion was more prevalent on the immersion surface. However, the pits on the salt spray surface showed larger surface areas, larger volumes, and covered more area on the micrographs as compared to the pits on the immersion surfaces, due to the pit debris that trapped chloride ions within the pits. Finally, it concludes that the AZ31B magnesium alloys are suitable for immersion conditions than salt spray environments.

Keywords

Magnesium Alloys, Immersion Tests, Salt Spray Tests, Corrosion Rate, Response Surface Methodology.

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