Tartaric acid cross-contamination in post-cascade rinses after sulphuric acid anodising (SAA): Effect on adhesive bond strength of AA6060-T6 alloy

The commercial feasibility of simultaneously running sulphuric acid anodising (SAA) and tartaric-sulphuric acid anodising (TSA) processes in the same anodising line was evaluated. Tartaric acid cross-contamination in communal cascade rinses after SAA or TSA processes may affect the adhesive bond strength of SAA-processed aluminium alloys for the automotive industry. In order to assess the commercial feasibility of running both SAA and TSA processes in the same anodising line, tartaric acid was introduced to post-SAA anodising rinse tanks (3 cascade rinses in total) prior to hydrothermal sealing. The adhesive bond strength of anodised AA6060-T6 coupons was evaluated by single-lap-joint tests in tension loading. Results indicated that tartaric-acid cross-contamination in post-SAA anodising rinses did not adversely affect the lap-shear strength of adhesively bonded AA-6060-T6 coupons, suggesting that both SAA and TSA processes could be potentially run in the same commercial anodising line by adding an extra tank for the TSA process followed by three communal cascade rinses prior to final hydrothermal sealing.