Formation and Properties of Zr/Ti Based Nano-Sized Non-Chromium Chemical Conversion Coating on AA 5083.

An environment-friendly non-chromium chemical conversion coating was obtained from fluozirconate/fluotitanate acidic solution for the corrosion protection of AA 5083. The surface morphology, composition, electrochemical behavior and corrosion resistance of this coating were investigated. The coating was found to be a homogeneous and dense layer consisting of nano-size particles, of which the major component was compound oxides consisted by Al, Mg, Zr, Ti, F and O. The results of electrochemical measurements, immersion and natural salt spray (NSS) tests demonstrated that the corrosion resistance of the AA 5083 H-116 was improved by the nano-sized non-chromium chemical conversion coating considerably, which was most attributed to the great inhibitive action on the anodic dissolution by acting as a protective barrier layer.