Galvanic corrosion of anodized 6061 aluminum alloy in an industrial-marine atmospheric environment

Abstract

6061 aluminum alloy is a material that is widely used for manufacturing aircraft. Boron-sulfuric acid anodization is often used in the surface treatment of aluminum alloy to improve the corrosion resistance of the alloy in an outdoor atmosphere. However, few studies have been conducted on the galvanic corrosion of an anodized 6061 aluminum alloy coupled with high strength structural steel in an industrial-marine atmospheric environment. In this work, the outdoor atmospheric exposure test of an anodized 6061 aluminum alloy coupled with 30CrMnSiNi2A steel of different surfaces was conducted in an industrial-marine atmospheric environment. The corrosion behavior and mechanism of the anodized 6061 aluminum alloy coupled with steel were investigated by means of electrochemical measurement, corrosion product analysis, mechanical property testing, fracture analysis, and other measurements. After a one-year exposure test, the values of strength σb and elongation δ of the anodized 6061 aluminum alloy coupled with Cd-Ti plated 30CrMnSiNi2A steel decrease by 6.45% and 4.39%, respectively and have the lowest decline rate compared with the most serious decline rates of 10% and 62.28%, respectively, for the anodized 6061 coupled with naked 30CrMnSiNi2A steel and the moderate decline rates of 6.77% and 10.74%, respectively, for the uncoupled samples. The intergranular corrosion and pitting on the surface of anodized 6061 aluminum alloy result in a significant decrease in the mechanical property, with the deepest crack of intergranular corrosion reaching 150 μm. The sulfide in Qingdao atmosphere not only corrodes the surface of the samples to form aluminum sulfate but also permeates into the grain boundary to promote intergranular corrosion.

Keywords

• anodized 6061 aluminum alloy
• galvanic corrosion
• industrial-marine atmospheric environment
• mechanical property
• intergranular corrosion