GB50316 specifies that galvanized thermal insulation materials must not come into contact with stainless steel pipes
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It is strictly prohibited for galvanized insulation accessories to come into contact with stainless steel pipes. Flange fasteners fall under the category of insulation accessories. There is a batch of stainless steel equipment currently in use – can galvanized fasteners be used with these stainless steel flanges? They will only be used for pressure testing and transportation during the production process, not for actual manufacturing. What effects might this have on the stainless steel in the short term?
When zinc comes into contact with stainless steel at high temperatures, it can cause the stainless steel to become zinc-sensitive and crack. Potential corrosion is minimal at room temperature. Theoretically, check valves can cause potential corrosion of zinc; therefore, they are used only for pressurization and transportation during processing, not in actual production. Short-term exposure does not cause corrosion of stainless steel. However, it is difficult to determine whether zinc will remain on the surface of the stainless steel after contact, which could pose safety risks in the future. It is advisable to avoid any contact between zinc and stainless steel.
References such as the National Textbook for Pressure Pipeline Designers and Approvers, Pressure Pipeline Design and Engineering Applications, standards SH3059 and GB20801, all stipulate that stainless steel must not come into contact with galvanized materials, as this can lead to potential corrosion. Risk of bimetallic (electrochemical) corrosion when stainless steel comes into contact with galvanized steel or aluminum: Bimetallic corrosion can occur only when two different metals are in electrical contact or when they are placed in a conductive liquid. The resulting \"battery\" will cause corrosion in one of the paired metals. Potential corrosion can occur due to pressure and handling during transportation; short-term exposure does not cause corrosion in stainless steel. However, it is possible that zinc may remain on the surface of the stainless steel after contact, posing a safety risk. Therefore, it is necessary to avoid contact between zinc and stainless steel.
I didn’t know it before, but now I’ve learned it!* ! ! !
Zinc is a reactive metal that loses electrons; it should be zinc that corrodes, not stainless steel. Could you please advise?