Hi,
HAS U A4 is stainless plate with stainless steel washer. Base plate of grade S355 is painted. Please confirm
1) if corrosion will take place between base plate and washer.
2) if yes then any rubber washer or any other means of separation is required? specification of separation material required for C5 corrosivity category.
Thanks for the interesting question and apologies for delay in reply.
In this scenario, I see the higher chances of bi-metallic corrosion and paint may not do justice to prevent the corrosion and time span to resist corrosion by paint will largely depend upon the surrounding environmental conditions. You may choose zinc coating as an option to increase maintenance time or V16S Stainless steel washers may also be used.
EPDM rubber washers shall help for achieving water tightness.
Another important aspect in question I observe that you are referring to CRC 5 which means the environment will be highly corrosive and there A4 material may also not have higher working life and 1.4529 (HCR) grade anchors are usually recommended.
Hope this answers your query. Feel free to reach Hilti Engineer for more technical queries by filling form : Anchor Design Services - Hilti India