A New Method to Investigate Localized Corrosion on 2024, 7075 and 6061 Aluminium Alloys in the Sea-Like Atmosphere Environments

Document Type : Research Paper

Authors

• S. S. Azimi Abarghoui
• A. Saatchi
• R. Ebrahimi Kahrizsangi

Abstract

Adding some alloying elements such as copper and zinc into aluminium and appling precipitation hardening process, makes these alloys sensitive to different types of corrosion in marine atmospheric environments. Precipitates on the matrix and grain boundaries are the main factor for corrosion. In order to study the corrosion behavior of metals in marine atmospheric environments, simulated environmental conditions is required to provide severe atmospheric environments containing chloride ion. In this research, a new method is used to study the atmospheric corrosion. At first specially prepared samples were tasted in corrosion cells with different time periods that the salt crystals were placed on the surface of samples and end grain areas on sample thickness were investigated. In this situation 100% relative humidity condition was stable. The microscopic studies showed that the intergranular corrosion happened less than 72 hours in 7075 alloy because of presence of deposits in grain boundaries and after this time, intergranular corrosion transform to pitting and exfoliation corrosion. Uniform corrosion with small pits was stable for 2024 alloy and the corrosion rate for 6061 alloy was lower than 2024 and 7075 alloys. Finally In order to compare the corrosion behavior of surface, the alloys were placed into the salt spray test for 672 hours according to ASTM B117. In this situation, 2024 alloy had the highest rate of corrosion.

Keywords

• Aluminium alloys
• Marine atmospheric Corrosion
• Intermetallic Compounds
• Intergranular Corrosion
• Exfoliation Corrosion

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