Brighter Aluminum Finishes from a Modified Chemical Brightening Solution

In North America, aluminum automotive trim and bumpers are chemically brightened in a phosphoric acid-nitric acid based solution, while in Europe a modification of this, which contains additives of sulfuric acid and copper, is being used. These two types of chemical brightening solutions have not been compared systematically for automotive applications.

This paper describes the chemical composition of the two chemical brightening solutions as well as the resulting image clarity and reflectance on AA-5252. AA-5657 and AA-7029. Results from laboratory and industrial plant trials are given which show the modified solution to be superior. The implications of converting to the modified solution, in terms of cost and waste acid handling, are discussed.