Iron-rich inclusion influence on the corrosion of the AA3003 aluminum alloy in concentrated nitric acid

Abstract

Aluminum alloys usually present high corrosion resistance in concentrated nitric acid due to an oxide film called passive layer formed on their surface. A heat exchanger made of aluminum AA 3003 alloy presented a strong localized corrosion in concentrated nitric acid, due to the presence of iron-rich inclusions. These inclusions are readily dissolved when the alloy enters in contact with concentrated sulfuric acid forming ferric ions. These ions are known as aluminum depassivator agents. Thus, the mentioned inclusions, when dissolved in nitric acid, caused a localized break down of the passive layer formed on aluminum, leading to corrosion. Therefore, the heat exchanger corrosion occurred due to the presence of elongated ferric ion reach inclusions. This of geometry favored the retention of the ferric-ion reach electrolyte. This work aims discussing the causes of corrosion of the heat exchanger.


Reference

PANOSSIAN, Z.; ALMEIDA, N. L.; SOUZA, E. F. M. Influência das inclusões ricas em ferro na liga de alumínio AA 3003, em ácido nítrico. In: CONGRESSO INTERNACIONAL DE TECNOLOGIA METALÚRGICA E DE MATERIAIS, 49. São Paulo, 1994. Anais… São Paulo, 1994. v.11, p. 217-231.


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