Improved Wet Strength Adhesion of Epoxy Coatings to Steel

Abstract

A method of treating steel before applying organic coating has been developed. This treatment provides not only corrosion protection under coatings, but also provides high wet adhesion strength between the epoxy polymer and a metal substrate. It involves a method of enhancing the adhesion of epoxies to steel substrates by organic modification of a tin wetting hydrosol (SNS Process). The wet strength adhesion has been determined by a 90° peel test for a variety of test conditions. Strip peel tests were conducted on CTBN rubber toughened, epoxy polymers coated onto cold rolled steel foil. The variations investigated were: a) after coating the substrate with epoxy (initial condition), b) after exposure of the coated part to an aqueous solution at 72±2°C for 24 h (wet condition), and c) following a 150°C bake to remove water from the sample. The adverse effect of water on adhesion for a series of metal treatments were examined.