Wrought and high-velocity oxy fuel sprayed Inconel 625 - examination of corrosion aspects

Metallic high-velocity oxy fuel (HVOF) coatings are increasingly being used to provide corrosion protection in process engineering environments. In th is paper the microstructural and corrosion characteristics of HVOF-sprayed Inconel 625 are considered and compared with wrought Inconel 625. Electroch emical techniques (a.c. and d.c.) have been used to characterize the corros ion behaviour of the coating and wrought alloy in static saline conditions at ambient temperature (18 degreesC) and at a higher temperature (50 degree sC). Galvanic corrosion tests between Inconel 625 and carbon steel have bee n conducted. Using a combined electrochemical monitoring and microstructura l examination methodology, it has been shown that HVOF-sprayed Inconel 625 suffers localized corrosion not evident on the wrought alloy. In addition i t has been demonstrated that no benefits in corrosion performance are gaine d by using a vacuum impregnation technique to seal the surface of the coati ng.