Corrosion improvement of AA7075 through precipitation hardness and anodization

Abstract Cast aluminum alloy (AA7075) has been precipitation treated and anodized in Tartaric-sulfuric acid (TSA). The effects of precipitation treatment and precipitation treatment plus TSA anodization on corrosion improvement of the cast AA7075 was investigated. The microstructure and morphology of the samples were studied using metallurgical microscope and scanning electron microscope with energy dispersive x-ray (SEM EDS). Weight loss method was used to access the corrosion behavior of the alloy in 0.5 M NaCl. Results obtained indicates significant role of precipitation treatment, precipitation treatment and TSA on corrosion improvement of AA 7075. The microstructure of the precipitation treated samples in palm kernel oil and SAE 40 engine oil showed precipitates of MgZn2. The anodic film coating of the precipitation treated in palm kernel oil plus TSA anodized sample recorded highest micro hardness value of 124.33 HV, while the least value of 178.67 HV was recorded for sample precipitation treated in SAE 40 engine oil and TSA. Precipitation treated and TSA anodized samples show higher corrosion resistance improvement, with the Palm kernel oil treated recording 22.05% corrosion penetration rate while Palm kernel oil treated and TSA anodized sample recorded 17.86% corrosion penetration rate.