Chromium-Free Coating System for DoD Applications

摘要

The objective of this project was to develop and test one or more primer systems that can be used on metals of interest to DoD, such as aluminum alloys, hot-dip galvanized steel (HDG), and cold-rolled steel (CRS). Primers are used as a basis for final paint systems on such metals. The corrosion protection of a painted metal comes primarily from the primer and not from the topcoat or the metal pretreatment under the primer. Therefore, the primer is a very important part of the integral paint system on a metal. Currently used primers contain organic solvents, chromate anti-corrosion pigments, and other undesirable components from an environmental standpoint. Thus, our intent was to develop a number of primer systems that were largely water-based and did not contain anti-corrosion pigments based on chromates. Since such anti-corrosion pigments are not readily available, we had to invent and develop some new pigments that are compatible with the proposed primers. Such pigments are different for the different metals on which the primer is applied. The basis of our proposed primer is the experience that we had at the University of Cincinnati during the period 1994-2000 with the use of organofunctional silanes for the corrosion protection of metals. The PI (Wim van Ooij) led a group of graduate students at the University of Cincinnati who were each assigned a metal substrate for which to design and thoroughly test a primer. The water- borne resin systems could be chosen from aqueous epoxy, acrylate, polyurethane dispersions, or mixtures of one or more resins. The co-PI (Dale Schaefer) led another group which was responsible for the scientific evaluation of the silanes used and subsequently of model systems consisting of films of silanes and resins. The third group was led by Guy Davis at Dacco SCI in Columbia, MD. This laboratory was responsible for exposure testing of candidate coatings by the B-117 and the Ford AGPE tests.