Cast Iron Keel preparation for Coppercoat

[Delfini]

I can see there are loads of related posts on this topic but I haven't really seen the reasoning behind most advice to do a proper job on a cast keel before epoxy and blast it to get rid of all rust and imperfections

I am being advised against blasting by the copper coat guy (he has done over 20 boats in coppercoat) who has seen quite a few decent looking keels turn out looking like the surface of the moon after blasting and most of the owners were less than happy - he also mentions a lot more prep work to get back to a workable surface after blasting and doesn't see the point

My cast keel is 20 years old and looks absolutely fine but its got a few layers of antifoul which need to be removed and he is suggesting to mechanically scrape and sand hard back to metal and then apply sealing epoxy prior to coppercoat

I would be interested in the general consensus here - is there a strong argument to blast a decent loooking keel or is it best practise ?

Thanks

 

[MoodySabre]

I had my 1988 Moody Coppercoated last year. The yard said it wasn't worth doing the keel is it wouldn't last and rust spots would come through. So they just blasted it and faired it and primed and antifouled it. 16 months later the boat was lifted and there are the usual rust spots that soon whizz off with a flap wheel and then AF. Just a quick job on a summer special lift with an hour in the slings. The boat stays in all winter so avoiding the costly lift and launch helps towards the cost of CC.

If your keel is looking good and is rust free and nicely smooth then I'd leave it as is.

 

[boatmike]

Tend to agree that it might well not last as long as on other substrates but preparation is everything. If the present coating is well adhered to the Iron then leave it but remove AF. If it's not then blast it and start again. Either way fill and fair to a smooth finish and give it several coats of epoxy before coppercoating to avoid problems later. DONT put coppercoat directly on iron......

 

[pmagowan]

I am not sure it matters all that much how you get your keel back to metal. I used a wire disk on an angle grinder and althoug it was hard work it did the job. I probably would have blasted it if I had the chance. The most important thing is to get the coating on good and quick. An uneven surface is not really a problem as you can just use a thickened epoxy to fair it. I have had no rust from my keel despite it only having normal antifoul. I used primocon and some underwater primer followed by about 4 layers of antifoul paint. preparation is the key but it should not be beyond the wit of man to encapsulate a keel.

 

[KellysEye]

If going back to bare metal the only way to stop rust coming back is coat or two of zinc rich epoxy. Also only go back to bare metal when the humidity is very low otherwise you risk flash rusting. Don't use wire brushes it leaves tiny bits of metal on the keel.

 

[KAL]

We blasted back to metal and it was alarming to see how rough a cast can be, but it was comforting to know that treating it with the proper stuff and epoxyi filling, fairing then 6 coats of epoxy before CC applied means that we should never have to do the job again.

 

[Champagne Murphy]

Year before last we blasted the keel, then several epoxy coats and finally coppercoat. All done professionally. After 7 months in the water it was rusting through in multiple places. We ended up blasting it again and using epoxy tar and conventional a/f.
It was a waste of money on a cast iron keel.

 

[vyv_cox]

My keel has been Coppercoated twice, each time by grit blasting, epoxy priming, fairing, followed by Coppercoating. The first treatment lasted about ten years before rust blew it all off. The second one has now been going for about eight years and small blobs of rust are appearing. The problem with grit blasting is that it removes a lot of the soft structure of the cast iron but with modern softer alternatives to aluminium oxide it should be possible to obtain effective cleaning without this damage.

 

[jordanbasset]

Can't help thinking the big advantages of copper coating is that you do not have to lift out each year for anti-fouling and also not have the mess and hassle of anti-fouling each year. If you are still doing that, okay only anti-fouling the keel, not sure if the cost of copper coating makes much sense. Or is there something I am missing

 

[rob2]

Well, that is possibly true if you have a cast iron keel, though Vyv's examples of the teatment almost lasting the life expectancy of the coating is interesting. Others with lead or fully encapsulated keels can reap the full benefits so long as they don't use a half-tide mooring. Once mud gets impacted onto the keel, no antifouling works!

At one time I sailed regularly on a friend's T24. It had a cast iron, bulbed keel which had been GRP coated, presumably polyester judging by its age, and rust had got beneath it. Every year more had to be ripped off until the best ploy was to chisel it all away and just prime and antifoul the bare casting. We often discussed the possible benefits of fairing and epoxy coating, but the British weather always stopped us as launch date approached.

Rob.

 

[IanR]

After 7 years of positive results following a sequence of failures using other solutions I finally resorted to Corroglass http://www.corrocoat.com/product/corroglass/ applied with a roller and spatula. The keel which had rusted regularly and which was nothing but scrap iron has been perfect since. The Coppercoat has not blown from the surface and the Corroglass has kept the iron protected. I found the product as I was searching desperately for something effective and discovered this product is used extensively in the North Sea and a oil industries.

Preparation is key with Chlor Rid which is added to the blast mixture and removes salt deposits from the iron keel as proved by a testing kit.

It's not cheap and a little complicated to apply but it sure beat the pants off Fertan and anything else I tried and boy I tried a lot before this.

I have not stuck my neck out up to now but figure that seven years is enough off a test.

No connection other than a very satisfied customer

 

[adambrickley]

After 7 years of positive results following a sequence of failures using other solutions I finally resorted to Corroglass Corroglass - Corrocoat applied with a roller and spatula. The keel which had rusted regularly and which was nothing but scrap iron has been perfect since. The Coppercoat has not blown from the surface and the Corroglass has kept the iron protected. I found the product as I was searching desperately for something effective and discovered this product is used extensively in the North Sea and a oil industries.

Preparation is key with Chlor Rid which is added to the blast mixture and removes salt deposits from the iron keel as proved by a testing kit.

It's not cheap and a little complicated to apply but it sure beat the pants off Fertan and anything else I tried and boy I tried a lot before this.

I have not stuck my neck out up to now but figure that seven years is enough off a test.

No connection other than a very satisfied customer

Hi Ian, just looking at coppercoating ballast keel. hull prepped and thinking about keel. I followed your link and found 4 products. Could you explain exactly which ones you used and roughly what the process is. I am going to chip back to hard metal, wire brush and use a rust converter first, then looking at a quality primer (corroglass sounds good) then copper coat. Is this roughly what you did? which product did you use?

 

[AndyL]

Tercoo it.

 

[neil_s]

Previous owner epoxied the bottom of my boat including the cast iron keel. I didn't know this - the keel was all rusty, lumpy and bumpy. When I came to clean the A/F from the iron, I found the layer of epoxy - with lots of tiny holes in it where the rust was leaking out. I would suggest that not even epoxy is a permanent rust preventative!