Oscillational corrosion potential of HastelloyC coatings fabricated by GS-HVOF spraying

Coatings of HastelloyC fabricated by HVOF spraying with a gas shroud (GS) have shown the superior barrier characteristic and corrosion resistance in seawater environment. During immersion of these coatings in artificial seawater, however, oscillation phenomenon of the corrosion potential was observed. In order to reveal and control the oscillation behaviour, some types of surface modification of the sprayed coatings and changing of the spray condition were carried out and their effect on the corrosion potential was investigated. The oscillation was caused by repetition of seawater penetration through surface oxides of the sprayed particles to their metal face and subsequent passivation of the metal. Such surface oxides were formed upon the stacking process of the sprayed particles on the substrate. Surface modification of the sprayed coatings and changes of the spray condition could reduce the oscillation effectively.