Hex Chromium-Free Sealants for Defense and Aerospace. 2014.
Polysulfide sealants containing soluble hexavalent chromium compounds are used in aerospace/defense manufacturing primarily for the filling of gaps and recesses to prevent water intrusion in an attempt to prevent corrosion of the base metal. Regulatory mandates have accelerated a global effort industry wide to replace hexavalent chromium containing materials because they are carcinogens, mutagens, developmental toxicants, and have high acute toxicity. The principal technical performance challenge for transitioning to hexavalent chromium free polysulfide sealants is twofold; the corrosion inhibiting properties of the hexavalent chromium free alternatives are not well understood, and the industry and military standards’ qualification tests do not adequately differentiate between hexavalent chromium containing and hexavalent chromium free formulations.