According to different processing methods, there are mainly dipping methods, paste methods, brushing methods, spray methods, circulation methods, electrochemical methods and other methods for pickling and passivation of stainless steel plates.
Dipping method
This method is most suitable for stainless steel pipelines, small elbows, etc., and the treatment effect of this method is the best. Therefore, the treated parts can be completely immersed in the pickling passivation solution, the surface of the stainless steel pipe fittings can be completely reacted, and the passivation film will be relatively uniform and dense. This method is suitable for continuous batches, but it is necessary to observe the reduction of the reaction concentration of the solution at any time and constantly add new solution. The disadvantage of this method 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 that are too long and too wide; if it is not used for a long time, the effect will be reduced due to the volatilization of the solution, etc., and a special site, acid pool and heating are required. equipment etc.
ointment method
The pickling passivation paste that can be used for stainless steel pipes has been widely used and a series of products are available. The main components are composed of nitric acid, hydrofluoric acid, corrosion inhibitors, viscous agents, etc. in a certain proportion, and there are specific inspection rules. Manual operation, suitable for on-site construction, suitable for welding seam treatment of stainless steel chemical containers, welding discoloration, dead corners, back of escalators and large-area smearing and passivation.
The advantage of the paste method is that no special equipment and site are required, and no heating equipment is required. The on-site operation is very flexible. The pickling and passivation can be completed at one time, and the independence is relatively strong. The passivation paste is one-time use, and the reaction will stop after a layer of passivation on the surface. It is not easy to be over-corroded, and it is not limited by the subsequent flushing time. The weak links such as welds can also strengthen passivation. The disadvantages are that the operating environment for workers 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, so it needs to be combined with other methods.
spray method
This method is suitable for pickling passivation of a single product in a fixed site, a closed environment, or equipment with a simple internal structure, such as the spray pickling process on a plate production line, and for stainless steel chemical containers, it can be used for pickling the inner wall of the container. The advantage of this method is that the continuous operation speed is fast, the operation method is relatively simple, the corrosion effect on workers is small, and the solution utilization rate is high. This method has many restrictions, such as no residues, impurities, etc. in the container; if the pickling solution stays in the container for too long, it will react and cause over-corrosion of stainless steel, so it must be operated continuously, and a large amount of cleaning water must be prepared at any time. Serious consequences will be caused in case of power outage, water outage, work stoppage, etc.; waste acid and waste water must be stored in larger containers; with the increase of reaction time and the increase of solution impurities, the effective components of the pickling solution will gradually decrease. Check the solution concentration and add new solution in time.
