passivation and pickling in SS storage tanks?

[jor1492]

Hi guys,
I have two questions about the surface treatment in a SS tank
1)For the construction of a SS storage tank, is necessary passivation and pickling? or only passivation could be enough for the construction?
2)What is the difference between the ASTM A 380 and A 967? I have to use one of them or the both for a passivation procedure?

Regards

 

[EdStainless]

2) There is a lot of overlap between A380 and A967. A967 was written to include some more modern practices.

What are you storing in the tank?
How oxidized are the welds?
I presume you selected SS for a reason. Oxidized welds will be very prone to localized corrosion.
I would hope that the major surfaces are very clean and free from oxides.
If the welds are discolored it would be worth cleaning them if you have any concerns about corrosion.
Typically people use a pickling paste to clean welds. Sometimes they do a light abrasive clean first, but it really the pickling that removes both the oxide and the Cr depleted layer of metal below it and restores corrosion resistance.
Passivation of stainless is a cleaning operation to remove embedded Fe from the surface. Every place that someone touched this material with a steel tool or set it on a steel support there is Fe in the surface. Passivation removes this and allows a good clean surface to resist corrosion. Nitric acid is fast and easy, citric acid needs t be warm and takes a bit longer to work but it is a lot easier to work with and dispose of.

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P.E. Metallurgy, Plymouth Tube

 

[jor1492]

Thanks EdStainless,
The tanks will store different kinds of reagents like NaSH, coagulants and others.
The tanks are not build at the moment. I am working in the construction specification for the contractor and now dealing with this topic of surface treatment for SS
In your experience what you think could cover the best this kind of work or what is the most common A380 or A967?