Keel rust spot - help please !

[ericw]

Hi !

Visited the boat yesterday for the first time since she was lifted out and noticed small area of rust on leading edge of keel.

Being new to the maintenance game could any of you guys offer any advice as to how I should go about treating this rust.
Guess I'll need to remove rust and treat before anti-fouling, but what's the proper method ? What products have worked for you in the past ?

Thanks in advance for your assistance.

Regards,

Eric.

www.HarryHindsight.com

 

[ccscott49]

Power wire brush, halfords or equivalent rust killer, 2 x epoxy keel primer, antifoul. IMHO

 

[AndrewB]

Cast iron or mild steel?

Cast iron usually suffers only from mild surface rusting which can be cleared with a power wirebrush.

Mild steel - the rust burrows into pits and all traces must be removed with an angle grinder or, if it is extensive, by grit-blasting. Otherwise it will continue to rust under the paint.

Rusting will accelerate out of the water so the quicker you get it treated and primed, the better. Don't use derust agents (phosphoric, oxalic or tannic acid) except as a temporary measure to hold the surface prior to treatment. Do use a zinc based primer, something like red zinc paint (conventional) or zinc-based epoxy (two-pack). Quick-dry primer will cure even in the winter.

 

[Fishbourne]

Try this technique - it has worked for me.

1. Remove as much of the rust as possible using wire brush, grinder etc.

2. Then mix up a small amount of epoxy resin and paint on over bare patch.

3. While this is still wet rub over the area with a medium abrasive paper (e.g. P120). This keys the epoxy on to the metal. Any bits end up in suspension in the resin and will do no harm. make sure you wear disposable gloves.

4. Once the resin has gone off rub it down and apply a second coat of resin.

5.The next layer of paint which could be antifoul or antifoul primer can be applied as soon as the epoxy has hardened and before if has formed a surface product. If there is a long gap (more than 4 hours) before the paint is applied then the epoxy should be wet sanded with a fine grade paper.

This process works on many metals. Any surface oxide is removed by the abrasive in step 3 whilst the epoxy resin prevents it from immediately forming again.

Has anyone else used this method? What have your results been like?

 

[oldsaltoz]

G'day ericw,

Cast Iron will "Flash Rust" so you must get a coating on as soon as you have cleaned it.

This is most important and missing from the posts to date. It will turn from grey (If sandblasted) to a brownish grey in minutes.

I Hope this helps.

Avagreatchristmas Old Salt Oz /forums/images/icons/cool.gif

 

[ccscott49]

Thats why I reccomended using a rust beater, converter or whatever, we use osphor, out on the rigs, it's wonderful stuff, phophoric acid I think anyway, steel treated with this stuff then painted with epoxy paint and antifoul, survives out here, in the splash zone, which is the worst place for corrosion for years, so a keel for half a year, should be OK. IMHO.

 

[TimLamb]

I've got an a quote somewhere from one of the main mags, basically it says rub it down, paint it over with a specialist keel paint from one of the main suppliers, then antifoul it.
The emphasis was very much don't worry and don't fuss - I'll try to find it and send you a more accurate details.

Tim

 

[philip_stevens]

I've used NeutraRust 662 in the past to excellent effect. I had my keels sand blasted five years ago, to remove flakes of rust. I then left the keels for 3 months to get some surface corrosion, before I applied the NeutraRust solution. It goes on looking like double cream, turns violet and then an enamel-looking black. I then put the anti-fouling over the black finish.

In the 5 years it has been on, no rust has shown through.

Now the downside. /forums/images/icons/frown.gif NeutraRust doesn't appear to be available in the UK in NeutraRust guise.
But /forums/images/icons/smile.gif..... Screwfix Direct have what looks to be the same stuff under another name. In my edition 68, it is on page 50, as Rust Converter, D18770-68 at £4.99 for a 250ml bottle. It goes a long way. It is water based, and quick drying, so a second coat could be applied soon afterwards. Also, it is fairly thick and will give a good smooth surface when dry - filling voids, etc..

regards,
Philip

 

[ericw]

Thanks for all your help, guys - much appreciated, as usual !

Regards and Happy New Year !

Eric.

www.HarryHindsight.com