Corrosion resistance of AA3005 laminates phospho-chromated with "rinse" and "norinse" processes

To reduce the environmental impact of surface chemical conversion processes, companies producing aluminum alloy laminates need to convert plants that use "rinse" technology, (i.e., processes that require rinsing after treatment surface in the conversion bath) to "no-rinse" (i.e., processes that do not need to be rinsed) with the aim of reducing the amount of water used in their processing cycles. At the same time, there is a need to eliminate hexavalent chromium (CrVI) from any type of industrial process, due to its known carcinogenic effects. In this study, therefore, the protective properties offered by specimens obtained from AA3005 alloy laminates, subjected to "no-rinse" CrIII-based phospho- chromate processes, both naked and painted, were studied, comparing them with those exhibited by specimens processed using the traditional CrVI-based "rinse" process. The experimental results have shown that the specimens treated with the no-rinse procedure involve a greater resistance to corrosion than those rinse treated. Therefore, the no-rinse CrIII-based treatments seem to be a valid alternative to the rinse ones, due to the increase in corrosion resistance of the material, the evident reduction of the environmental impact, as well as the reduction of the costs of process.