The Effect of Chromium and Manganese Addition on the Corrosion of As-cast Al-Si-Fe-Cu Alloy System in Caustic Soda

• Main Authors: S.A. Yaro, V.S. Aigbodion
• Format: Article
• Language: English
• Published: al-Farabi Kazakh National University 2008-01-01
• Series: Eurasian Chemico-Technological Journal
• Online Access: http://ect-journal.kz/index.php/ectj/article/view/686

The effect of chromium and manganese addition on the corrosion of Al-Si-Fe-Cu alloy system in caustic soda (NaOH) at room temperature (28 °C) was investigated using weight loss method. The alloys containing 0.1 to 0.3% Cr and Mn were produced and sand cast into cylindrical test bars at the foundry shop of the National Metallurgical Development Center, Jos. After casting the microstructures of the as- cast alloys were determined. The as-cast test bars were machined to corrosion coupons and immersed into 0.5M NaOH solution and their rate of corrosion determined using the weight loss method. It was observed that  simultaneous addition of chromium and manganese to the alloy system imparted the highest corrosion resistance to the alloy due to the formation of hard and passive phases which acted as strong protective barriers to corrosion. While addition of chromium alone to the alloy gave a better corrosion resistance than the addition of manganese alone due to the formation of passive oxide layer of chromium oxide.