The Hydroelectric Power Plants have, among their auxiliaries, the hydro mechanical equipments such as: trash racks, inlet gates, draft tube gates, bulkheads and stoplogs.
In a general manner, the gates (skin plate, girders, trunnions girders, wear plates, struts, end frames) are manufactured with structural steel ASTM A36 or ASTM A572.
For seal plates and bolts, the material is 304 stainless steel.
In this context, with stainless steel bolts and nuts it exist a small cathode area relative to a large anode area (the structural plates) and a bimetallic corrosion should be a minor issue in the absence of an electrolytic; but, in the environment of hydropower plants, besides the occasional immersion, the rain water or the humidity of the air acts like an electrolyte.
From the document "Design of Spillway Tainter Gates", page 8-1
(U S Army Corps of Engineers. Engineering and Design. EM 1110-2-2702 1 January 2000) it can be read:
"......Where dissimilar metals are in contact, rubber gaskets or equivalent insulators should separate them. Generally, this is not necessary for stainless steel bolts, because the area of contact between the bolt and structural steel is very small".
Is it or is it not necessary any insulation (paint, polymer, etc.) to avoid the direct contact between the threads of these materials?
Thanks in advance for your comments.
El que no puede andar, se sienta.