Iron Keel Rusting

[MASH]

The cast Iron keel of my Sadler is rusting in a patch about the size of a tea-towel. This has become significant as it is exfoliating.

How to treat it? Tools, materials and techniques please!

 

[30boat]

It could be a casting inclusion or just normal rust.The best tratment is griblasting and priming imediately after the surface is bright.That's usually not practical so the best next thing will be grinding the rust off,cleaning the dust thoroughly and priming.This won't be 100% effective but will give you a finish that you can maintain every by tending to the small areas of rust that will surface.

 

[capt_courageous]

Hi
I had the same problem on the keels of my Griffon. Tried all sorts of things, Primocon etc which did not work well. Last winter I cleaned them back as best I could and put on Hammerite paint and some anodes. Certainly seems to work with the best results so far. Hammerite works very well on my gates at home so I gave it a try on the boat.

 

[lw395]

Grind/disc sand rust off.
Jenolite or other phosphoric acid treatment.
Allow to dry.
Get it as warm as possible. Work on a small area with a hot air gun.
This will also get surface as dry as possible.
Brush on a small amount of west epoxy.
Heat with hot air gun.
Sand with 80 grit wet and dry. This get the epoxy into the surface as well as possible.
When set, another coat of epoxy or two.
fill will epoxy based filler.
Antifoul and start saving up for a boat with a proper lead keel!

 

[rudolph_hart]

There are a few tips here http://www.ybw.com/forums/showthread.php?t=254223

 

[ghostlymoron]

You'll never completely solve this problem as iron and seawater are an unholy combination. Last year I removed all surface coatings using a wire brush on an angle grinder and recoated immediately with 2 coats of Primocon then antifouled over this. Seems to be lasting well although patch treatment will be needed soon. Previously I had wire brushed by hand and applied Hammerite primer - this didn't last well.
Take care when wire brushing with an angle grinder as the wire bristles tend to fly out sometimes - best to wear overalls, gloves and goggles. Grit blasting is the best but could cost around £300 apparently. Preparation of the bare metal substrate is essential as no subsequent coating will compensate for a poor foundation.

 

[Ruffles]

2 years ago I used an angle grinder with a flapper wheel. Then a couple of coats of neutrarust followed by two coats of an epoxy primer. The primer was NOT cheap but since I'd just stripped the anti-foul off the hull I thought I'd do a proper job.

After 2 years in the water it looks ok. Just a couple of coin sized patches.

 

[Evadne]

The whole of my 1963 cast iron keel is like this. I paint it with antifoul each year, occaisionally chipping off exfoliating bits, and trust that the dimples are like those on a golf ball, and make us go faster than the smooth finish would. It certainly doesn't attract any more fouling than the (smoother) grp.

 

[Bosun Higgs]

Had a Hunter bilge keeler and got frustrated by this problem. So I cleaned both keels back to bare metal and coated one with epoxy tar and the other with chlorinated rubber paint as used on big boats. The chlorinated rubber worked really well.

The best answer by far is to remove the keels and send them to the galvaniser for pickling and coating.

 

[Bobobolinsky]

Galvanising is no good permanently immersed. It just corrodes away, it needs air to form a stable coating. Processes are blasting and coating, best, followed by power brushing. Sanding and grinding tend to smear the iron and don't remove the contamination

 

[BAtoo]

Option 1 - Grit-blast & IMMEDIATE coating with epoxy, tie coat, AF. Lasts a long time if its done right. Have had 1 keel done this way but only in Yr2 so cant comment on this ones durability.

Option 2 - Scraper and sander, hammerite, tie coat & AF. Lasts maybe 2 years before some patches re-appear. Have done 2 keels this way.

Option 3 - flake off the worst, slap on some AF (+/- tie coat). Lasts 1yr.

As in life you get what you pay for........