1. Before shot blasting and rust removal, the 304 stainless steel pipe should be preheated to remove moisture. The preheating temperature is 40℃~60℃;
2. Rust removal should reach Sa2.5 level in GB/T8923 "Steel Surface Rust Level and Rust Removal Level before Painting", and the depth of anchor marks on the surface of 304 stainless steel pipe is 40μm~100μm;
3. The remaining rust and dust on the surface of 304 stainless steel pipes should be removed;
4. Spraying should be carried out within 4 hours after surface pretreatment.
In addition, there are two main methods for galvanizing the surface of 304 stainless steel pipes: hot-dip galvanizing and electro-galvanizing. Hot-dip galvanizing includes wet method, dry method, lead-zinc method, redox method, etc.
The main difference between different methods of hot-dip galvanizing is how to activate the surface of the pipe body to improve the quality of galvanizing after acid leaching cleaning of 304 stainless steel pipes. Dry method and redox method are mainly used in current production.
The surface of the zinc layer of electroplated galvanizing is very smooth and dense, with a uniform structure; it has good mechanical properties and corrosion resistance; the zinc consumption is 60% to 75% lower than that of hot-dip galvanizing. Electro-galvanizing is technically complex, but this method must be used for single-sided coating, double-sided coating with different coating thicknesses on the inner and outer surfaces, and galvanizing of 304 stainless steel pipes.
