The NF T35-509-7-2012 standard specifies the preparatory process for steel substrates prior to application of coatings and related products, in particular the test method for non-metallic shot peening abrasive treatment. Part 7 focuses on the determination of water-soluble chlorides and aims to evaluate the presence of water-soluble chlorides on the surface of shot peening steel substrates that are harmful to coatings. The standard describes in detail the test procedures, reagent use and data processing methods. The presence of chlorides may lead to reduced adhesion between the coating and the substrate, which in turn affects the long-term performance of the coating. Through the implementation of this method, the surface condition of the substrate after shot peening can be effectively monitored, the adhesion and durability of the coating can be ensured, and the painting mass and anti-corrosion effect can be improved.