Paint for steel floors?

[joliette]

Can anyone suggest a good paint to apply on steel floors? I've tried hammerite overcoated with bilge paint, but I have some floors where it has not adhered as well.

This appears to be due to some form of electrolysis taking place in the floors forward of the (aluminium) mast which is keel stepped, but I don't know for sure.

All of the other floors are fine i.e. no sign of the same reaction to the hammerite. It goes without saying that all of the floors are fitted with galavinsed steel bolts, not stainless, so I can't understand it!

Anyway, I thought that I would try coating with neat epoxy this time.

All suggestions and ideas welcome.

 

[Peterduck]

Have you re-galvanised the floors recently? If not, I would strongly recommend it. If nothing else, it will provide a sacrificial coating of zinc which will prevent the electrolysis from removing valuable steel. Epoxy won't give you this. Even more preferable is to track down the cause of the electrolysis, but this could be worse than the proverbial needle in a haystack. If you have recently re-galvanised the floors, then you may need to etch them with a weak solution of Spirits of Salts [a.k.a. Hydrochloric acid] to give a surface that the paint can adhere to. You should be able to buy this at any builder's supply shop, as it is used to clean old mortar from brickwork. Further, I would use a zinc-rich metal primer ["Cold Galvanising"] over the real galvanising, as I don't believe that you can have too much of this stuff.
Peter.

 

[joliette]

The problem with re-galvanising is that the 4 or 5 floors concerned pass between the keel and the keelson, upon which the mast is stepped. So, extracting the floors for re-galvanising would require some major deconstruction. The condition of the floors is good, with only light surface corrosion, so I thought that (for now) I'd try to find a coating which is better than hammerite. Maybe I'll give zinc-based primer a try.

 

[burgundyben]

There a zinc rich primer called Galvafoid that I've used in the past and been very impressed with, the tin is very heavy hich I think is a pointer to the zinc content.

 

[Mirelle]

Another vote for Galvafroid. It is a very soft paint and won't tolerate the least abrasion, though.

Re-galvanising does not always work; I've been told that wrought iron floors sent in for re-galvanising could not be treated because of the buildup of chlorides in the interstices of the metal. Mild steel may be less of a problem, but if the Hammerite is not staying on then I suspect salt contamination.

A very silly point, perhaps, but if the bilges are normally dry, corrosion is much slower. Since I sorted the deck out with Coelan, Mirelle's bilges have been dry apart from the stern tube drip in the sump (one stroke of the pump, per week). One effect of this is that the floors don't rust.

A possibly unrelated thought, but the floors that I would sort out first are those in way of the mast step. Mirelle started leaking when bashing to windward through bumpy stuff, and investigation showed a whole catalogue of horrors in the mast step area. Coroded floors, forgotten keel bolts, rotten mast step, rot in frame heels....it was not quite clear what was holding all this together - in the most highly stressed part of the boat!

Seven new floors, four new frames, one new mast step and quite a lot of £ later, she is a reformed character and will bash to windward in a breeze for longer than her owner will, with no visible symptoms at all.

 

[aztec]

i'd vote for galvafoid too, used it many times on metal tanks, chassis etc. better than other cold galvy' paints.

 

[snowleopard]

International Primocon is designed for underwater ironwork so should do a fair job.

 

[ccscott49]

There is a special hammerite primer for zinc etc. Used for garage doors and the like, excellent stuff, adheres well. Then overcoat with hammerite, should do the job, I also give a vote to galvafroid, but getting difficult to find these days.

 

[Vara]

Haven't used it but ZINGARD reads well, I found this while mooching about the Duff site so no doubt it is a tad expensive.

 

[joliette]

The first coat of Galvafroid went on this afternoon. It was very easy to brush on and does look good. The solids took quite a lot of stirring into the solvent. I must find out what solvent is used because the PAINT FUMES down in the bilge went straight to my head - much worse than with hammerite - and it was good to get out in the fresh air after that! So, really important to get a good draft going through the boat before you use this stuff.

 

[AlexHall]

Agree with Galvafroid, if you ever need to do it again, try a surface tolerant ferrous metal epoxy primer, followed by a cold tar epoxy. The big thing with old wet and or contaminated metal is the primer. I used Sigmacover 280 follwed by TCN300 below waterline and in bilge on my own 33'steel gaff cutter but before, did so at work on 30meter motoryacht of same material about 10years ago. Superb stuff and remarkable price difference from yacht paints. Neat epoxy will not adhere to much unless it can be absorbed. Sigmacover 280 was created to be applied over steel which was hydrojetted and still wet!