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.

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Since cracks often initiates at the interface and propagate along the interface for materials with dissimilar interfaces such as metal/metal and polymer/metal, such as thermal sprayed materials, coated steel sheets and semiconductor packages, evaluation of interfacial strengths are an important issue for the reliability of these materials. However, it is difficult to evaluate the interfacial strength of such materials when they are subjected to the same tensile tests as homogeneous materials, because in many cases a mixture of interfacial and base material fracture occurs. Currently, the most common methods for evaluating the interfacial strength of these materials are to conduct strength tests by introducing a pre-crack at the interface or to test for crack propagation from the interfacial edge, wherein the interfacial strengths have been evaluated by parameters that define the stress singular fields at the interfacial crack or the dissimilar edge. We overviewed methods for evaluating the strengths of the dissimilar interfaces based on these stress singularity parameters.

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