Novel Pretreatments of Metals for Corrosion Protection by Coatings: Part I, Plasma Polymerized Hexamethyldisiloxane on Cold-Rolled Steel
By van Ooij W. J. & D., Conners K.
1998
Abstract
In an attempt to replace metal pretreatments that produce toxic by-products with more environmentally friendly treatments without sacrificing the degree of corrosion protection, the use of plasma pretreatments and plasma-polymer films has been investigated. Cold-Rolled Steel (CRS) panels were treated in a plasma of oxygen or a mixture of argon and hydrogen, or both sequentially. A film of plasma-polymerized hexamethyldisiloxane (PPHMDS) was then deposited in the same plasma reactor. The panels subsequently had a cathodic E-coat applied over the PPHMDS. These panels, a phosphated CRS panel, and an untreated CRS panel, were then subjected to a cyclic accelerated environmental corrosion test, after which they were tested using Electrochemical Impedance Spectroscopy (EIS). The EIS tests were also conducted over an extended period of time, during which the panels were continuously exposed to a 1.0 M solution of NaCl. The results indicate that under certain pretreatment conditions, PPHMDS, when used as a primer for E-coating, can perform as well or better than standard phosphating.