A novel de-rusting method with molten salt precleaning and laser cleaning for the recycling of steel parts

Steel parts are a kind of high recovery value product for which de-rusting is the primary step in the recycling process. Laser cleaning is a popular and effective de-rusting technique at present. However, the rust on most end-of-life/used parts is very serious, and it is difficult for laser cleaning to remove it all. Therefore, a compound cleaning method was proposed in which molten salt was first used for the pretreatment of rust, followed by laser cleaning. It was shown that the rust layer after pretreatment was much easier to remove with low laser fluence. The cleaning efficiency could be improved by at least 1.34 times, and a cleaner surface without any damage could be obtained. This was the result of the inner-to-outer cleaning effect of molten salt. The penetration into the rust layer and the decomposition of the doped organics caused the contaminant layer to be destroyed in the interior and then peeled off sheet by sheet. The composition and structure analysis indicated that the remaining rust layer was oxidized, and it became looser after molten salt cleaning, which made it easier to clean. The application of molten salt to the cleaning of rusty parts will improve de-rusting efficiency and promote the development of de-rusting techniques effectively. It provides a feasible and high-efficiency choice for de-rusting.