Analysis of admiralty brass corrosion products in sea water and brackish water

Abstract

A method was developed for the separation and analysis of corrosion products formed on admiralty brass surfaces immersed in sea water at 40 °C and pH 8.2. This method is based on the selective dissolution of various oxidation compounds with suitable solvents (i.e., that dissolve the metal matrix to only a negligible extent). These analyses can be performed in oxidation films of more than 10 nm thickness. The following solvents were used: (1) methanol to dissolve Na⁺, Cu²⁺ and Zn²⁺ chlorides and sulphates; (2) glycine to dissolve bivalent metal compounds—Cu²⁺ and Zn²⁺ oxides, oxysulphates, oxycarbonates; and (3) ammonia solution to dissolve Cu⁺ compounds.

Reasonable agreement between the results of X-ray analyses and chemical analyses was observed only for copper and zinc compounds, which are the main constituents of the corrosion products. The presence of tin compounds in the corrosion products was observed with chemical analyses, which yielded quantitative results, but was not observed with X-ray diffractometric analyses. The chemical methods can therefore either integrate the results obtained with other methods or be complementary to them.