Effects of chromate and chromate conversion coatings on corrosion of aluminum alloy 2024-T3

Abstract

Various effects of chromate conversion coatings (CCCs) and chromate in solution on the corrosion of AA2024-T3 and pure Al are studied in this work. Raman spectroscopy was used to investigate the nature of chromate in CCCs through a comparison with the spectra of known standards and artificial Cr(III)/Cr(VI) mixed oxides. Chromate was shown to be released from CCCs and to migrate to and protect a nearby, uncoated area in the artificial scratch cell. However, experiments investigating the effect of chromate in solution on anodic dissolution kinetics under potentiostatic control indicated that large chromate concentrations were needed to have an effect.

Accelerated growth of oxide film on aluminium alloys under steam: Part II: Effects of alloy chemistry and steam vapour pressure on corrosion and adhesion performance

“…Although banned today due to carcinogenic issues [8], chromate-based conversion treatment [9] is the most protective conversion coating due to the re-passivation provided by the self-healing ability of chromate. A number of alternative conversion coatings are in use, however none of them have been proven to be as good as chromate-based conversion treatments.…”

Corrosion protection of AA 2024-T3 aluminium alloys using 3, 4-diaminobenzoic acid chelated zirconium–silane hybrid sol–gels

“…This is important if the alloy contains high levels of secondary phase particles, such as copper intermetallics, which may promote galvanic activity. The current state of the art for protecting aluminium alloys involves the use of hexavalent chromium technology in the form of conversion coatings and pigmented anticorrosion primers [1]. However in the interest of human health [2,3] and environmental concerns, alternative solutions are being pursued.…”

A study of the mechanisms of corrosion inhibition of AA2024-T3 by vanadates using the split cell technique

“…Debate still exists regarding the control over the anodic dissolution of active phases [33]. Nevertheless, the fast and irreversible formation of the Cr 3+ layer seems to play the major role [20,33,34]. In addition, chromate systems exhibit the critical property of self-healing or active corrosion protection.…”