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Passivation of stainless steel elbow by pickling

1: Impregnation Method

Stainless steel pipes, elbows, small pieces, etc. are suitable for this method, and the treatment effect is good. Because the treatment 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 should be replenished continuously with the decrease of reaction concentration. Its disadvantage is limited by the shape and capacity of acid tank, not suitable for large capacity equipment and shape too long and too wide pipeline; Long-term use will be due to volatilization of solution and other reasons and the effect will decline, need special site, acid pool and heating equipment.

2:Preparation Method
Stainless steel pickling passivation paste has been widely used in China and has a series of products supply, main ingredients by nitric acid, hydrofluoric acid, corrosion inhibitor, viscous agent according to certain proportion of ship mark "stainless steel pickling passivation paste" CB/T3595-94 have specific inspection rules, the manual operation, suitable for site construction, ship weld stainless steel chemical processing, welding discoloration, top deck  Parts, corner corners, the back of the escalator and large areas of passivation in the tank are applicable.

The advantage of the paste method is that it does not need special equipment and site, stainless steel elbow does not need heating equipment, flexible field operation, pickling passivation is completed once.Strong independence;Passivation paste has a long shelf life, each daub treatment with a new passivation paste one-time use, the surface of a layer of passivation after the end of the reaction is stopped, not easy to over corrosion, not subject to the subsequent washing time limit, weld and other weak links can also strengthen passivation.Disadvantages are poor operating environment, high labor intensity, high cost, the treatment effect on the inner wall of stainless steel pipeline is slightly poor, need to combine with other methods.
3:Spray Method
Suitable for a fixed site, closed environment of a single product or the internal structure of the simple equipment pickling passivation.  For example, the spray pickling process on the plate production line can be used for pickling the inner wall of the cargo tank on the stainless steel chemical ship.Its advantages are fast continuous operation, simple operation mode, little impact on corrosion of workers, pipetting process can be the pipeline pickling again. The solution utilization rate is high. 


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