1993 Volume 42 Issue 3 Pages 144-151
A new portable controlling-atmosphere spraying system was developed to deposit metallic coatings with an excellent performance against wet corrosion. Characteristics and corrosion performance of the coatings deposited by the arc or flame spraying of high Cr-Ni wire in the controlled argon gas were examined and compared with that of the coatings deposited by the conventional spraying in air. Among the coatings, the coating deposited by arc spraying in argon gas was found to be dense without oxides and pores, and possess the alloy composition same that of the spraying wire. Polarization measurement of the coatings in sodium chloride and hydrochloric acid revealed that the anti-corrosion resistance increased in the order of (1) flame spraying in air, (2) arc spraying in air (3) flame spraying in argon (4) arc spraying in argon. Corrosion resistance of the coating deposited by arc spraying of wire in argon gas was improved to a great extent. In hydrochloric acid solution, even the spraying wire suffers slight active dissolution. Therefore, the coating deposited by the arc spraying in argon gas suffers pitting corrosion associated with small pores and crevice corrosion along the paths in the coating. Corrodant slowly penetrates into the coating.