Stress Corrosion-Cracking and Corrosion Fatigue Impact of IZ-C17+ Zinc-Nickel on 4340 Steel

New protective material could replace cadmium and aluminum coatings on critical components.

Naval Air Warfare Center, Patuxent River, Maryland

The protection of cathodic metallic materials used for aircraft components, like 4340, Aermet 100, and PH 13-8 corrosion-resistant steel, is critical to keeping the steel from pitting and cracking due to exposure to the operating environment. Two important properties are resistance to stress-corrosion cracking (SCC) and corrosion fatigue. These are insidious failure mechanisms that can lead to part failure in service.

Cadmium and aluminum coatings are currently used to protect high-strength steels from corrosion, pitting, and cracking. These coatings are applied on new components and also at Navy Fleet Readiness Centers (FRC) during component repair and overhaul. Both are effective but each has shortcomings.