Pickling and Passivation for SS weld joints

It depends.
What material? What Aramco spec? How is it welded?

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P.E. Metallurgy, consulting work welcomed

I looked through the SAES 2005 copy related to piping and welding and could not find any requirements whatsoever for pickling of SS after welding.

Passivation is used in austenitic to create an homogeneous oxide layer to prevent air exposition corrosion. Soaping the surface of welds with nitric or citric acid creates a very thin layer of oxid and dissolves free iron from surface, wich seems to be benefecial for the SS.

Passivation of SS is a cleaning process mostly to remove free Fe from fabrication and handling.
The Passive surface fill of oxide on SS forms naturally and only need a clean surface.
Picking uses more aggressive acids, nearly always with HF to actually break down the heavy oxides from weld or HT and also to dissolve the layer of Cr depleted metal below it.

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P.E. Metallurgy, consulting work welcomed