wp1234
Well-Known Member
Ive got some rust around some swim platform bolts and just wondering what I could coat on top of them to protect this season - does clear waxoyl ( the car underseal stuff )work I wonder and is it safe to use on gelcoats?
Rust protection vs GRP
- Thread starter wp1234
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oldsaltoz
Well-Known Member
Are the stainless bolts 316 grade?
VicS
Well-Known Member
I assume you mean the Waxoyl rustproofing solution, although what I have is not exactly clear. It's messy, dirt sticks to it and I would not trust it to not stain the grp.
If you have rust stains appearing around fasteners it's a pretty sure bet that the joint needs resealing to keep water out or you'll find that they are being eaten away by crevice corrosion. That should then stop the rust stains.
Oldsaltz' point about them being 316 is valid but I dont know how he would advise distinguishing 316 from 304.
If you have rust stains appearing around fasteners it's a pretty sure bet that the joint needs resealing to keep water out or you'll find that they are being eaten away by crevice corrosion. That should then stop the rust stains.
Oldsaltz' point about them being 316 is valid but I dont know how he would advise distinguishing 316 from 304.
oldsaltoz
Well-Known Member
As it's only the swim platform I imagine the bolts are not large in size or number, as Vic pointed out you may have some corrosion already.
Why not just replace them with 316 stainless and seal them when replacing the new bolts.
You can remove the rust stain with a number of products, the rapid ones are acid based and should not be allowed to dry on the area being treated.
Avagoodweekend......
Why not just replace them with 316 stainless and seal them when replacing the new bolts.
You can remove the rust stain with a number of products, the rapid ones are acid based and should not be allowed to dry on the area being treated.
Avagoodweekend......
ccscott49
Well-Known Member
304 is magnetic, 316 isnt!
VicS
Well-Known Member
[ QUOTE ]
304 is magnetic, 316 isnt!
[/ QUOTE ] You sure about that. Aren't they both austenitic?
304 is magnetic, 316 isnt!
[/ QUOTE ] You sure about that. Aren't they both austenitic?
srp
Well-Known Member
[ QUOTE ]
Oldsaltz' point about them being 316 is valid but I dont know how he would advise distinguishing 316 from 304.
[/ QUOTE ]
Usually the 316 bolts have A4 on the head - (should be embossed, not stamped, as that way it's a sure bet that the lettering was done by the manufacturer). 304 will have A2 on the head. If there is no marking, it's either a lower grade altogether, something specially manufactured or not stainless.
I agree with Vic on the Waxoyl, marvellous stuff but you don't want it on your gel coat. Just buy new A4 bolts from somewhere like Anglia Stainless or A2A4.co.uk. I would use a bit of Sikaflex or similar around the bolt head/ washer to seal it.
Oldsaltz' point about them being 316 is valid but I dont know how he would advise distinguishing 316 from 304.
[/ QUOTE ]
Usually the 316 bolts have A4 on the head - (should be embossed, not stamped, as that way it's a sure bet that the lettering was done by the manufacturer). 304 will have A2 on the head. If there is no marking, it's either a lower grade altogether, something specially manufactured or not stainless.
I agree with Vic on the Waxoyl, marvellous stuff but you don't want it on your gel coat. Just buy new A4 bolts from somewhere like Anglia Stainless or A2A4.co.uk. I would use a bit of Sikaflex or similar around the bolt head/ washer to seal it.
vyv_cox
Well-Known Member
304 and 316 are non-magnetic, as Vic says they are both austenitic. 304 is also known as A2, 316 as A4, as has already been said. 400 series stainless is magnetic, this is the stuff that cutlery, sinks, many other supposedly 'stainless' items, are made from, usually between 5 and 13% chromium but little or no nickel. Its big advantage is that being ferritic/martensitic, dependent upon carbon content, it can be heat treated. So high strength stainless bolting, for example, will usually be 400 series.
Unfortunately, although 316 stainless is better than 304 for both pitting and crevice corrosion, it is not completely immune. As has been suggested, filling the crevice with a sealant such as Sikaflex 291 usually solves the problem. Even a gasket of plastic cut from packaging or something similar may well do the job.
Unfortunately, although 316 stainless is better than 304 for both pitting and crevice corrosion, it is not completely immune. As has been suggested, filling the crevice with a sealant such as Sikaflex 291 usually solves the problem. Even a gasket of plastic cut from packaging or something similar may well do the job.