Is this considered potential corrosion between the bolt and the flange?

Last edited by Front Row Viewer on 2020-4-10 09:35: The catalyst to be restructured

Atmospheric corrosion! ! Change material! !

Why doesn’t the nut below seem to have much corrosion?

As can be seen from the figure, if the bolt and the flange are not made of the same material, galvanic corrosion can occur when exposed to moisture or steam. Furthermore, as can be seen from the figure, the nut on the upper part of the same bolt is more severely corroded than one on the lower part, mainly due to the influence of the pipeline’s insulation layer. The waterproof layer of the insulation structure is leaking, causing the insulation material to become wet. In this way, the water in the insulation layer (the corrosive agents in the insulation layer + water) can cause electrochemical corrosion of the bolts, and such corrosion is quite severe. Suggestion: Ensure the insulation layer is waterproof ； When selecting bolts, they must be of the same material as or similar to that of the flange ； The protection method using bolts can be adopted.

Received. Ensure good waterproofing; if the strength is sufficient, replace with stainless steel bolts. If alloy steel bolts are used instead, carry out proper anti-corrosion maintenance. Thank you to the moderator