- Before shot blasting and rust removal, 304 stainless steel pipes should be preheated to remove moisture, and the preheating temperature should be between 40 ℃ and 60 ℃;
- The rust removal should reach Sa2.5 level in GB/T8923 “Rust Grades and Rust Removal Grades of Steel Surfaces before Painting”, and the depth of anchor lines on the surface of 304 stainless steel pipes should be 40 μ m～100 μ m;
- The residual rust dust on the surface of 304 stainless steel pipes should be removed thoroughly;
- Spraying should be carried out within 4 hours after surface pretreatment.
In addition, there are two main methods for surface galvanizing 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 what method is used to activate the surface of 304 stainless steel pipes and improve the quality of galvanizing after acid immersion cleaning. Currently, dry and redox methods are mainly used in production.
The surface of the zinc layer on the galvanized surface is very smooth and dense, with a uniform structure; Having good mechanical properties and corrosion resistance; Zinc consumption is 60% to 75% lower than that of hot-dip galvanizing. Electrogalvanizing has a certain degree of technical complexity, but it is necessary to use this method for single-sided coatings, double-sided coatings with different thicknesses of inner and outer surface coatings, and 304 stainless steel pipe galvanizing.