Hydrogen Embrittlement and Stress Corrosion Cracking of Titanium Alloys Caused by Cleaning Processes

Hydrogen was absorbed by titanium alloys in an alkaline scale conditioning bath. This absorption was initiated by an iron/nickel contamination on the areas to embrittle. If the hydrogen exceeds 500 ppm H chipping under load occurs. Hydrogen absorption can be completely prevented by removal of the iron/nickel contamination in a nitric acid solution prior to scale conditioning.

Vapour degreasing of titanium alloys in trichloroethene or tetrachloroethene does not have a negative effect on the subsequent welding processes. It is not expected that vapour-degreased titanium components will suffer from stress corrosion cracking under later load (stress and temperature), for example in the engine. Only stabilised trichloroethene may be used for vapour degreasing titanium components under stress. Components at 80 % rupture load suffer from stress corrosion cracking when vapour degreased with tetrachloroethene.