SBIR-STTR Award

Use of chromates as corrosion inhibitors in coatings, adhesives and sealants is a well established technology. However, toxicity and waste disposal problems have led to the urgent need for development of an environmentally benign substitute for chromium compounds in coatings and sealants, which is the subject of this SBIR. This paper discusses the state-of-the-art technical approaches to the solution and suggests: (1) Grafting of metal surface with "surface active agent", such as quaternary chelating agents and gianidines to passivate potentially active corrosion sites on the metal surface. (2) Converting the metal oxide layer, which is formed as a corrosion product on the metal surface, into a protective layer for the surface beneath. The paper also discusses material selection criteria, formulation hypotheses, and proof of concept testing for the development of a non-toxic and environmentally safe inhibitors to be used in chemical conversion coating of aluminum and aluminum alloy (MIL-C-5541), primer coating of metals (M1L-P-23377), and corrosion inhibiting sealing compounds (M1L-8-81733). Future development efforts, as well as developmental directions in optimizing corrosion resistant properties, are suggested.

Chromium containing compounds, used as additives to paints, coatings and sealants, have provided unsurpassed corrosion protection of metal surfaces over the past few decades. In more recent years chromates and other heavy metals have been shown to pose significant health risks and are now targeted for elimination. Many potential alternative corrosion inhibitors have been advanced by government, industry, and university laboratories. These alternatives are typically not as effective as chromates or they require more significant processes to accomplish equivalent protection. The Phase I research investigated a novel approach to provide corrosion protection in a primer coating for metals, chemical conversion coating of aluminum, and corrosion inhibiting sealing compound. This research demonstrated the feasibility of this approach and resulted in candidate inhibitors for each material that provided equivalent corrosion protection to chromate containing reference materials. This Phase II effort will incorporate statistical design of experiment strategies to optimize the combination and levels of these corrosion inhibitors to maximize the corrosion protection afforded by a primer coating for metals, chemical conversion coating of aluminum, and corrosion inhibiting sealing compound. Each of these optimized formulations will be subjected to full qualification testing per Military Specification requirements, and will be submitted for Qualified Products List certification.