Is it necessary to acid wash and passivate stainless steel equipment and pipelines?
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I would like to ask: Is it necessary to carry out acid washing and passivation for stainless steel equipment and pipelines in order to prevent corrosion? From what I’ve learned, acid washing is done using low-concentration acids, while passivation is carried out with high-concentration acids. It seems that the passivation layer might be damaged under acid-washing conditions. The pH level under normal operating conditions for such equipment and pipelines is between 4.5 and 6.5; would the passivation layer be damaged under these conditions? If so, then it wouldn’t serve any purpose. I would appreciate it if experts could clarify whether this is indeed the case, and if there are any relevant standards. Thank you!
Stainless steel equipment has been pickled before leaving the factory, and no pickling or passivation is required after it arrives for installation. As for stainless steel pipelines, acid washing and passivation are generally not necessary, but in some special units, passivation is required.
It seems, I really remember it clearly – in the past, foreign specification sheets required that stainless steel pipes be pickled and passivated. In China, however, efforts were made to avoid such steps whenever possible. The exact wording in China’s GBT14976 states that steel pipes should be delivered after heat treatment and pickling; copper pipes that have undergone overall grinding, polishing, or heat treatment in a protective atmosphere can be delivered without pickling.
No need; it has been done before leaving the factory. Any damage caused by welding requires the weld area to be pickled again
Re-perform pickling and passivation to remove the passivation film. If system cleanliness is a concern, the system is acid-washed after the welding work is completed