Scientific Understanding of Non-Chromated Corrosion Inhibitors Function.

摘要

This project generated understanding of the mechanisms of non- chromate corrosion inhibiting coating systems by studying cross-cutting issues and leading chromate-free chemicals and systems. In Task 1, Trivalent Chromium Process coatings were found to release chromium into solution, which can then form a film on nearby uncoated alloy surface. Transient formation of Cr(VI) was observed, and postulated to form by oxidation of Cr(III) oxide by locally produced H2O2, which is a product of oxygen reduction. Inhibition in solution by common species found in commercial chromate-free primers was studied: molybdate, silicate, and praseodymium in Task 2, and Ce3+, Pr3+, La3+ and Zn2+ cations in Task 3. A mechanism for inhibition by each species was postulated. In Task 4, effects of surface treatments and roughness on adhesion of coatings were studied using the Blister Test. In Task 5, solubility of modern chromate- free pigments was found to depend on reactions with their environment and with their internal co-pigments, and their transport properties were influenced by ionic current and the fine structure of the primer matrix. Interactions between the various components of Cr-free coating systems were studied in Task 6. In Task 7, Direct Optical Interrogation was used for in-situ monitoring of metallic thin film corrosion underneath organic coating systems.