A product improvement program (PIP) for the surface finish of some steel military hardware has been recently initiated by the Navy. Presently the metal cleaning methods, interior and exterior surface finishes and corrosion protection requirements for such hardware are specified in MIL-P-18948. The coated hardware are stored in a warehouse structure for long durations. Because these storage places are not environmentally controlled (that is, no temperature or humidity control) the corrosion protection has not been adequate. The exterior surfaces of the hardware are coated with a corrosion inhibiting alkyd primer coating (TT-P-664) or a rust inhibiting lacquer primer coating (MIL-P-11414) to a thickness of 0.4 to 0.6 roils. The exterior color paint, (MIL-E-52891 or MIL-P- 11195), is applied to a thickness of 1.5 roils. The investigation of various coatings to replace the present system is an ongoing effort. The coatings have been examined from a corrosion protection vantage point and results have been correlated. The coatings were evaluated by exposing them to natural marine atmosphere and seawater wetdown tests. The coatings were also exposed to a 5.0% sodium chloride solution in a laboratory environmental salt fog chamber for 500 hours. Selected coatings were examined using Electrochemical Impedance Spectroscopy (EIS). The results obtained from field tests, salt fog, and EIS measurements are discussed.
Keywords: coatings, corrosion control, electrochemical impedance spectroscopy, atmospheric exposure field tests, salt fog exposure- steels alloys, military hardware, water uptake ratio