Effect Of Grit Blasting On Corrosion Resistance Of Thermal Spray Coating

The pore structure of the thermal spray coating makes the coating prone to corrosion failure.At present,the penetration of corrosive liquid is mainly controlled by regulating the structure and composition of the coating.However,after the penetration of the corrosive liquid into the substrate,the effect of the substrate surface condition on the corrosion resistance of the coating has not been effectively considered.In this paper,the material used was the atmospheric plasma sprayed alumina coating deposited on the surface of 45 steel substrate.The influencing factors,influencing mechanism and optimization schemes of grit blasting process on the corrosion resistance of thermal spray coatings were studied.The main works and conclusions obtained are as following:(1)Taking the grit particle properties,grit blasting parameters,and cleaning process after grit blasting as variables.The prepared coatings were subjected to a hydrochloric acid immersion corrosion test.The results showed that the size of the grit,blasting pressure,blasting distance,and the grit cleaning process are the main factors affecting the corrosion resistance of alumina coating.(2)Macro-observation and micro-characterization of the alumina coatings in hydrochloric acid immersion corrosion were carried out.The results showed that hydrogen gas generated by the reaction of hydrochloric acid with the steel substrate is the main reason for the peeling failure of alumina coating.Larger substrate roughness can reduce the contact reaction between the etching liquid and the substrate.Less grit residue will reduce the crack growth.And larger bonding strength can slow down the peeling of the coating.(3)The blasting parameters of different coating systems were quantitatively optimized using data statistics and multiple linear regression.The grit cleaning process was optimized by the combination of air purging,brushing and ultrasonic cleaning.And the optimizing effect of mixed blasting of different types and sizes of grit on the blasting quality and coating performance was verified.