Corrosion protection of cold-rolled steel by low temperature plasma inter-face engineering .1. Enhancement of E-coat adhesion

An anode magnetron enhanced d.c. cathodic plasma treatment of a cold-rolled steel (CRS) plate and cathodic (plasma) polymerization were used to create interface engineered systems of cathodic E-coat/plasma polymer/plasma treated CRS. The adhesion of the E-coat and the corrosion protection characteristics of the systems were compared with the control, E-coat/Zn phosphate-chromate/electro-galvanized steel (EGS). The adhesion of the E-coat to the plasma polymer coated CRS was found to be excellent; the E-coat could not be removed by N-methyl pyrrolidone (60 degrees C) in 5 days, while the same E-coat applied on the control was removed in a few minutes. The plasma polymer of trimethylsilane (TMS) was found to yield excellent corrosion protection as used in the interface engineered systems, of which the corrosion (GM scab) test was found to be better than that for the control. The plasma pretreatment of the CRS surface prior to the cathodic polymerization of TMS was found to be a critically important factor. The corrosion-induced delamination of the first paint layer seems to play a key role in the corrosion of painted steel. Tt was demonstrated that good adhesion and durability of the entire interface system can produce a highly corrosion resistant painted CRS.