工业海洋大气环境下阳极氧化6061铝合金的电偶腐蚀行为

在青岛典型的工业海洋大气环境下,进行硼硫酸阳极氧化6061铝合金与不同表面状态的30CrMnSiNi2A结构钢偶接件的户外大气暴露试验,通过电化学测试、腐蚀产物分析、力学性能检测、断口分析等,研究了偶接件中阳极氧化6061铝合金的腐蚀规律与机理.结果表明:经1 a户外大气暴露试验后,与镀镉钛结构钢偶接的6061阳极氧化铝合金力学性能最优,其强度σ_b和延伸率δ分别比原始试样下降6.45%和4.39%,远优于与结构钢裸材偶接的阳极氧化6061铝合金试样(分别下降10%和62.28%),略优于未偶接试样(分别下降6.77%和10.74%).沿晶腐蚀和表面点蚀是导致阳极氧化6061铝合金力学性能下降的主要原因,最严重的沿晶腐蚀裂纹深度达150 μm.青岛大气中的硫化物不仅会侵蚀试样表面形成硫酸铝,还会浸入到晶界促进沿晶腐蚀. 

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

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 σ_b 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.