Preparation of iron keel

[Dimond]

Hi All,
I'm ready to epoxy my 26' mirage and I have cleaned down her iron keel with a grinder to remove blistering rust. My question is do I need to seal it with something before I epoxy her. All suggestions welcome.

/forums/images/graemlins/confused.gif

 

[oldsaltoz]

G'day Sean,

I assume this is cast iron, grinding is not the best prep as the action leaves contamination on the surface, sand blasting will remove it.

As you will have seen, cast iron will 'flash rust', that is, it will start to change colour in a matter of minutes. Cast forms it's protective oxide coat, not good in salt water so you need to apply some protection as you go, not later the same day for best results or you are sealing in rust.

The method I have used in the past is as follows, for what it's worth I started using this about 8 or 10 years ago and have done a few keels since with no problems on any of them to date.

The sandblaster works from one end of the keel, starting at the top and running down the edge only, then moves to clean the next strip in line with the first one, as soon a strip wide enough for painting with a 2 inch brush is cleaned it is coated with a zinc based paint, this dries very fast and must be between 70 and 90 microns thick (this may vary with brands) too thin and it won't work, too thick it will mud crack; a small tin card with notches is used to measure the depth, very cheap and easy to use. follow the sand blaster as each strip completes get some protection on.

When this has completed I apply a coat of epoxy resin, when it is very tack a second coat is applied, this is then left to cure overnight.

The next step is to give the epoxy coat a very light sand, just enough to remove the shine, a 250 grit is good for this, a wipe with some acetone and plenty of clean white cotton rags and it's ready for a top coat.

I use International Interzone, it's the stuff they spray onto steel piles in harbours, lasts for years, after it has cured, a light sanding and on with the antifoul and your done.

I hope this helps

Andavagoodweekend............

 

[philip_stevens]

Re: Preparation of iron keel - with Neutrarust.

So as not to rewrite it all again, have a look at my post at http://makeashorterlink.com/?B47B517AA

and the follow-up at
http://makeashorterlink.com/?M14B227AA

If you need photos, let me know by PM, to show the result.

 

[KREW2]

Re: Preparation of iron keel - with Neutrarust.

HI
I am about to tackle an iron keel the rust is not flaking the keel is mostly rusty coloured slightly pitted with a lot of antifouling firmly in place, a scraper is out of the question and a wire brush has little effect, do I have to get all the antifouling off before I can use a rust converter?any advice on this matter may be ignored if involves too much hard labour thank you

 

[Petercatterall]

Re: Preparation of iron keel - with Neutrarust.

Sounds just like mine!
I have given up trying to do a 'proper' job (as being described in this thread!!) it has in the past taken me ages and the results have been dissapointing.
The last few seasons I have just gone over the keel with a drum sander (coarse paper) just to remove the high spots (ie the rusty blister bits) then a coat of 'paint for rusty metal' then anti foul.
Total time about 2 hours. It doesn't seem to be getting worse season by season.
Regards

 

[Porthandbuoy]

Re: Preparation of iron keel - with Neutrarust.

I hired a needle gun and it shifted everything back to bare metal almost as well as shot-blasting would have done. 2nd step was to paint with West epoxy and sand it 'wet' with medium grit emery paper. More epoxy applied while 1st coat was still tacky until final coat using 'peel ply'. Rip off the peel ply, apply antifoul primer and then antifoul.
Don't forget to use all the correct safety gear though.

 

[ashanta]

I your keel is very badly rusted I would shot blast it and then apply the recommended number of coats of blakes Keel prime. I have done this on previous boats and my current boat and the results have been excellent. I just deal with any isolated rust if and when it appears by use of a wire brush and more keel prime before antifouling.
Regards.

Peter.

 

[Robin]

My personal choice would be NOT to use epoxy for this job because keel castings can rarely be prepared completely enough. Shot blasting dry followed by immediate painting might just work, a ground or wire brushed or disked finish won't. Most castings are porous to varying degrees, there are some seriously crap ones about too and whatever you try rust will come back and lift the epoxy - then it really is hard work. My choice over many years, keels and boats has been to scrape/grind it clean, derust with a liquid like kurust then apply multiple coats of International Primocon. Primocon is simple to apply and forgiving of conditions and you can put on 2 coats per day on a good weather day, antifoul adheres very well (it is the primer for it as well as metals) and it is easy to maintain in later years plus it is cheaper than epoxy.