onesea Posted July 30, 2021 Posted July 30, 2021 (edited) Some may know I have bought a boat, others may note my caution around stainless steel on my motorbike... I don't have a picture of full layout but: cast metal anchor (CQR your for those in the know) - shackle - swivel - shackle - anchor chain. Both shackles pins secured with stainless steel to stop them undoing. Both shackles corroded I would say beyond use.. Cast anchor also corroded beyond use, swivel and chain ok... IMHO an extreme example of electrolysis and the same will happen where ever there are dissimilar metals... Including your bike (just much slower), so becarefull in your use of S/S Edited July 30, 2021 by onesea 2 Quote
JustinW Posted July 30, 2021 Posted July 30, 2021 Couldn't it be simply that the shackle has rusted in the salt water? The chain is almost certainly galvanized which would explain why it hasn't corroded. Quote
husoi Posted July 30, 2021 Posted July 30, 2021 Depends on the SS grade. For sure that is nothing close to SS 316 or SS316L will be the most common grade that have a higher resistance to corrosion and that provides a good durability. These are known as Austenitic steels https://www.ulbrich.com/blog/overcoming-saltwater-corrosion-with-stainless-steel/ further info https://nickelinstitute.org/media/1667/designguidelinesfortheselectionanduseofstainlesssteels_9014_.pdf Quote
Davidtav Posted July 31, 2021 Posted July 31, 2021 You could try using Monel seizing wire to secure the shackle pins … or actually just use plastic zip ties and change every season. That’s what I do. 1 Quote
onesea Posted July 31, 2021 Author Posted July 31, 2021 11 hours ago, JustinW said: Couldn't it be simply that the shackle has rusted in the salt water? The chain is almost certainly galvanized which would explain why it hasn't corroded. Cannot tell but shackle was probably galvanised, given there linked and common use they will all of been in salt water for similar amounts of time.. 34 minutes ago, Davidtav said: You could try using Monel seizing wire to secure the shackle pins … or actually just use plastic zip ties and change every season. That’s what I do. Must admit I replaced with new shackles and used cable ties. I was just amazed at the corrosion on the 2 shackles compared with the rest of the system. Although how long they had been in place I don’t know, could of taken a decade to get that bad for 4 years she has been left standing on the hard. I was just highlighting the problems S/S can create. Quote
Jerry1111 Posted July 31, 2021 Posted July 31, 2021 On 30/07/2021 at 22:01, husoi said: Depends on the SS grade. For sure that is nothing close to SS 316 or SS316L will be the most common grade that have a higher resistance to corrosion and that provides a good durability. These are known as Austenitic steels https://www.ulbrich.com/blog/overcoming-saltwater-corrosion-with-stainless-steel/ further info https://nickelinstitute.org/media/1667/designguidelinesfortheselectionanduseofstainlesssteels_9014_.pdf IMO depends more on galvanic potential voltage than SS grade. On it's own A2 will rust with time in salt water, A4 (316) will stay for long. But if you connect it with any other metal, it just depends on galvanic corrosion. IIRC its ok to have SS and Al (most of masts are done like that), but you don't want SS anywhere near zinc. I suspect that's the OP's problem. Quote
husoi Posted July 31, 2021 Posted July 31, 2021 I would be tempted to experiment with SS316 and nickel plating on top. Quote
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