Suggestion of a New Repair Technique for Steel Structures by Low-Pressure Cold Spray and Laser Cleaning

The effectiveness of a corrosion repair technique consisting of laser cleaning and cold spraying was investigated. The effect of laser pulse frequency on the removal of surface corrosion on steel specimens was analyzed. Subsequently, a zinc coating was cold-sprayed on specimens cleaned of surface corrosion using conventional disc grinder and laser methods. Furthermore, salt spray tests were conducted to compare the corrosion protection performance of the zinc coating on these specimens. The results showed that laser cleaning can effectively remove surface corrosion and that a laser pulse frequency of 15 kHz is more effective than that of 40 kHz for removing the surface oxide layer. A comparison of cold-sprayed zinc coatings on laser-cleaned and non-treated specimens indicated that surface oxidation during laser treatment may negatively affect zinc deposition efficiency. The zinc coating on the laser-cleaned specimen was more than twice as thick as that on the conventionally cleaned specimen, and the coating–specimen interface maintained good adhesion after a 168 h salt spray test. Although no corrosion was observed in both steel specimens after the salt spray test, cracking of the remaining corroded areas on the substrate and delamination of the coating occurred in the conventionally cleaned specimen.