PREVENTION OF WATER STAINING OF ALUMINUM

摘要

Protective compositions useful for protecting aluminum and aluminum alloy products against water staining and methods for providing such protection are provided herein. The protective compositions are solutions, in an inert aliphatic or aromatic hydrocarbon diluent having a 100.degree.F. viscosity of 20 to 100 SUS, of at least 0.1 weight percent of a protective composition having a hydroxyl value greater than 15 and derived from: (a) an aliphatic or cycloaliphatic polybasic acid containing from 18 to 72 carbon atoms and 2 to 4 carboxyl groups, and (b) a polyol partial ester derived from a C12-C22 aliphatic monocarboxylic acid and a polyol selected from the group consisting of aliphatic polyols and ether polyols obtained by the condensation of two or more aliphatic polyol molecules or by ethoxylation, the polyols containing from 3 to 30 carbon atoms and 3 to 22 hydroxyl groups, with not more than 70% of the available hydroxyl groups esterfied, the weight ratio of (a) to (b) ranging from 20:1 to 1:4. This composition not only has good compatibility with commonly used diluents, but also provides a protective film that can be removed by subsequent annealing. The method involves applying to the aluminum or aluminum alloy sheet, in neat form, n continuous film of at least 0.5 milligram of the protective composition per square foot.