Pre-treatment for pickling and passivation: The presence of grease and other contaminants on the stainless steel surface will affect the quality of pickling and passivation. Generally, alkaline detergents should be used to clean the inner wall of the tank.
Pickling solution / paste and the control of chloride ion concentration in cleaning water: Excessive chloride ion content will damage the stainless steel passivation film. Some stainless steel pickling solutions / paste use hydrochloric acid, perchloric acid and other corrosive media containing chloride ion as the main agent Auxiliary agents remove the surface oxide layer, which is unfavorable for preventing corrosion, and should be controlled during the inspection, as specified in the ship's standard "Stainless Steel Pickling Passivation Paste" CB / T3595-94 Control within the range of 25ppm ~ 100ppm. In addition, for the cleaning water, the chloride ion content should also be controlled below 25PPM. Adding chloride ion corrosion inhibitor sodium nitrate to the tap water during construction can meet the requirements.
Environmental protection of waste liquid neutralization: For the treatment of pickling and passivation waste liquid, it should meet the national environmental protection discharge requirements. For example, the waste liquid containing fluorine can be treated with lime milk or calcium chloride, and the waste liquid containing chromium can be added with sulfuric acid Iron reduction treatment, etc.
