chrishelen
N/A
Would it be ok to use a stainless steel backing plate on a galvanized bolt?both will be above the water line but open to the weather and splashes of sea water.
Stainless
- Thread starter chrishelen
- Start date
pyrojames
Well-Known Member
Not recommended.
chrishelen
N/A
why not?thats what i want to know,is it because the stainless will eat the galvanised bolt?
tillergirl
Well-Known Member
Nigel Warren's book says that 304 and 316 is compatible but 'may lead to to some lcoal corrosion of fitting around fastener'. I used to have galvanised rigging screws at the end of stainless steel rigging. Some rust appeared on the rigging screws which very limited but unsightly. Changed now more because of appearance than anything else. If you want to fit and forget, match them up.
chrishelen
N/A
Thanks for that,it just that i have lots of stainless offcuts lying about and my bowsprit eyebolt on the end of a galvanized chain which goes through the stem just above the water line needs replacing,but i will use mild steel plate instead,i wont get that galvanizes because of the cost,i think you can some sort of spray on stuff.
Bajansailor
Well-Known Member
Re your plate just above the waterline - this is where the corrosive elements are most ferocious really, and a piece of mild steel plate sprayed with 'cold galvanising' (ie zinc rich) paint is not going to last very long.
Rather than having the steel plate go rusty quickly, why not have a galvanised shackle joining the bobstay chain to a stainless steel plate on the stem?
OK, the galvanised shackle might wear more quickly than if the plate was mild steel, but it will be easier to replace.
Rather than having the steel plate go rusty quickly, why not have a galvanised shackle joining the bobstay chain to a stainless steel plate on the stem?
OK, the galvanised shackle might wear more quickly than if the plate was mild steel, but it will be easier to replace.
chrishelen
N/A
The galvanised eyebolt is about 8inches long by 1/2 inch dia,at the moment it goes through a mild steel plate screwed to the stem and then through the stem post just above the water line,attached to this eyebolt is a galvanized shackle ataching the galvanized bobstay chain,all i want to do is replace the mild steel plate with a stainless one,BTW the plate is3x6 inches.
Bajansailor
Well-Known Member
I would be inclined to replace the mild steel plate with a stainless steel plate and attach the chain with a S/S shackle - OK, this might accelerate the rate of corrosion of the chain links in way of this S/S shackle, but you could perhaps lavish some extra zinc rich paint on the chain in this area, to help the existing galvanising.
A section of galvanised chain will usually be more heavily galvanised that a galvanised shackle - at least that is how it seems to me. Galvanised shackles at the sea / air interface dont seem to last too long here before they start rusting!
A section of galvanised chain will usually be more heavily galvanised that a galvanised shackle - at least that is how it seems to me. Galvanised shackles at the sea / air interface dont seem to last too long here before they start rusting!
sandeel
Well-Known Member
Mild steel will just weep rust what ever you do, as you have some stainless offcuts then go for the stainless backing plate IMHO. Have a look here on the classic marine site which suggests a stainless fastener is acceptable.
galvanic corrosion
galvanic corrosion
chrishelen
N/A
Thanks,i will use the off cuts and use a stainless shackle, i will dip the end of the chain in my special dip i have concocted,as far as i can make out the existing set up has been in place for 10 years so i think the stainless will be fine.
Adamastor
Well-Known Member
Special dip???? TELL ALL!
