According to different operation methods, pickling and passivation of stainless steel mainly includes 6 methods such as dipping method, paste method, brushing method, spray method, circulation method and electrochemical method.
1. Immersion method. This method is more suitable for stainless steel pipelines, elbows, and small pieces. And the processing effect is ****. Because the treated parts can be fully immersed in the pickling passivation solution, the surface reaction is complete, and the passivation film is dense and uniform. This method is suitable for continuous batch operation, but new solution needs to be continuously replenished as the reaction concentration of the solution decreases. The disadvantage is that it is limited by the shape and capacity of the acid tank, and it is not suitable for large-capacity equipment and pipelines whose shape is too long and wide; if not used for a long time, the effect will be reduced due to the volatilization of the solution and other reasons, and special venues, acid pools and heating equipment are required.
2. The ointment method. Stainless steel pickling passivation paste has been widely used in China and has a series of products. It is manual operation and suitable for on-site construction. It is suitable for welding seam treatment of stainless steel chemical containers, welding discoloration, corner dead corners, escalator backs and large-area smear passivation. Be applicable. The advantages of the paste method are that it does not need special equipment and venues, no heating equipment, flexible on-site operation, pickling and passivation is completed at one time, and strong independence; the passivation paste has a long shelf life, and a new passivation paste is used for each application treatment. After the passivation of the surface layer is over, the reaction will stop, it is not easy to be corroded, and it is not limited by the subsequent flushing time. The weak links such as welds can also strengthen the passivation. The disadvantage is that the worker's operating environment is poor, the labor intensity is high, the cost is high, and the treatment effect on the inner wall of the stainless steel pipeline is slightly poor, and other methods need to be combined. Senyuan brand stainless steel pickling passivation paste does not contain hexavalent chromium and adopts formula. There is a RoSH report issued by SGS. After passivation, the corrosion resistance of the stainless steel workpiece can be increased to more than 10 times, and it can pass the standard salt spray test for 500 hours. The passivation process is a complete chemical reaction, which will generate a complete, dense and non-destructive passivation film on the surface of stainless steel. Applicable to all 200 series and 300 series austenitic stainless steels, mainly for larger stainless steel frames or workpieces that are not easy to soak, such as: 316, 317, 201, 202, 204, 303, 3012 302, 304, 305, 309, 314, 321, 347, XM7, XM15J1, 430, etc.
3. Spray method. It is suitable for pickling and passivation of single product in fixed site and closed environment or equipment with simple internal structure. The advantages are that the continuous operation speed is fast, the operation mode is simple, the corrosion effect on workers is small, and the solution utilization rate is high.
There are many restrictions on this method, such as: ① There shall be no residue or impurities in the container. ② If the pickling solution stays in the container for too long, it will react and cause excessive corrosion of stainless steel. Therefore, continuous operation is required, and a large amount of cleaning water must be prepared at any time. In case of power failure, water failure, or shutdown, it will cause serious consequences. ③ Waste acid and waste water must be stored in larger containers. ④As the reaction time increases and the impurities in the solution increase, the effective components of the pickling solution gradually decrease. The concentration of the solution must be checked at any time and new solution must be replenished in time.
