SS piping with threaded broze valves 2

[MechP]

Hello everyone,
I'm doubtful on material compatibility for a piping project compliant to ASME B31.3. Threaded bronze valves are to be installed on stainless steel pipe A-312 carrying crude water. As for corrosion between materials, is there a justification per standard ASME or ASTM that allows or forbids such instalation?
Thanks

 

[EdStainless]

Nothing in the Codes or standards, just good engineering practice.
What is the conductivity of the water? Temp, pH, and TDS also.
If the water is corrosive then you will likely have galvanic issues, especially since the area of the weaker alloy is relatively small compared to the more noble.

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P.E. Metallurgy, Plymouth Tube

 

[MechP]

Hi Ed,
Thanks for your reply. Exact water conditions for this case are unknown, however it should not be a of great concern since it is obtained from a clean river at 20ºC.
My primary concern is the interaction between stainless steel and bronze.

 

[EdStainless]

The water is the electrolyte, and it is a critical part of the circuit.
If this was very clean water (pH=7.5, TDS<100ppm) then I wouldn't worry, but river water will have higher conductivity and it will serve to promote the galvanic corrosion.
Find better valves. Alloys such as Ni Bronze, Ni-Al Bronze, and a few others are robust enough that they would work without concern.

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P.E. Metallurgy, Plymouth Tube

 

[Compositepro]

It is not something I would worry about. I have seen brass ball valves used with most pipe materials and never observed any particular galvanic corrosion problems. Brass and stainless are not far apart in the galvanic series, and stainless gets its corrosion resistance from an insulating oxide layer. It is important to remember that to get ion flow requires more that just any voltage over zero.

 

[moltenmetal]

I concur with Compositepro's assessment in relation to the combination of brass/bronze and stainless steel ONLY. River water will be a continual source of oxygen and you may get de-zincification of the brass valves over the long term, but stainless tends to be a weak participant in a galvanic couple in our experience. Personally I wouldn't worry about it. But if it were river water, galvanized steel pipe and brass/bronze valves, I'd be very concerned and I would expect severe localized corrosion of the galvanized steel.