Treating rust on iron keel

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Pavalijo

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Each year I power wire-brush off the rust which affects maybe only 10% of the keel's surface area and then treat it with Fertan or similar. I have then used up to 5 coats of Primocon before antifouling.
After 5 or 6 months in the water the rust appears just as before.
I know that I need to do something more radical to get rid of the rust and am only trying to slow its development down, but someone told me that Primocon is not the product for that purpose - so what should I use?
Many thanks
Paul
 
I also treat my cast iron keel with fertan (or similar), then one thickish coat of Teamac Metaclor underwater primer, then two thick coats of antifoul. That lasts two years.
 
Aeolus said:
I also treat my cast iron keel with fertan (or similar), then one thickish coat of Teamac Metaclor underwater primer, then two thick coats of antifoul. That lasts two years.
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Thanks, I may try that, and a bit more time on removal, and see how I go
 
Cast Iron is not an entirely consistent product. The quality is a very moveable feast.

The best stuff cleans up well by surface abrasion and will coat ok, but the poorer quality stuff has enough inclusions to make both cleaning and coating a bit of a lottery.

The good stuff that is well cleaned, dried and primacon-ed should last more than a few months.
 
I have tried just about every steel treatment going over 40 years having an originally galvanised mild steel lift keel plate, am on my second keel as I didn't know how to look after the first one, for a start like any lift keel boat by having the boat on high trestles to allow access to the plate.

The treatment which stands head and shoulders above the rest is

Dulux Metalshield

I know ' Dulux ' sounds like a joke but this is seriously good stuff, the keel looks almost as good on autumn lift out as when she is launched.

It's one part paint but requires the special Metalshield primer.

Best applied on bare metal as it can pickle other paint.

Available from places like Brewers - no connection apart from happy keel owner.
 
I tried for years to seal my old Sadler keel with Primocon and never had any luck, however much effort I put into preparation. I solved the problem with Hammerite and after using this only had to deal with a few small spots each year. This was back in the '90s and I believe that Hammerite is no longer up to the job but it does show that using the right stuff, such as the above, can save a lot of work.
 
johnalison said:
I tried for years to seal my old Sadler keel with Primocon and never had any luck, however much effort I put into preparation. I solved the problem with Hammerite and after using this only had to deal with a few small spots each year. This was back in the '90s and I believe that Hammerite is no longer up to the job but it does show that using the right stuff, such as the above, can save a lot of work.
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I have used the smooth on my lawnmower deck & its stayed put over the past yr
 
Interesting suggestions, Dulux metalshield and Hammerite.
From Dulux website I see that Dulux metalshield is a range of products. Which one was used?

I has been thinking of Primocon (and similar products from Seajet, Jotun, etc) more as primers for good adhesion, and only poor to moderate protection, as they are 1-component and never get as hard and dense as cross linked epoxy and PU paint. The website describes Primocon as suited for under water surfaces, but I doubt it is the best for rust protection.

I have trouble with rusty keel, too, and have read literally hundreds of posts in different fora about this problem. Still confused, I could not extract any consensus. It probably boils down to a combination of proper pretreatment, using a good product - at suitable conditions. Fail at any of the three, and you have to start over again next year.
Especially the last of the three can ruin a good plan. I like to sail in the summer, not grinding keel. The nasty keel job is postponed till autumn or spring, when the risk of water condensation on the cold iron keel is high.

This autumn I added a zinc anode on each side of the keel. Used Seajet 011 as it was too cold for epoxy primer.
 
If you go to Brewers or similar Metalshield is just one product.

As with everything in life preparation is everything...

I found Primocon and especially modern Hammerite about as much use as thinned toothpaste.

Metalshield is your answer, I temped in a chandlery and tried all the stuff going inc Blakes Steel Treatment, the car ' rust resolving ' stuff and Galvafroid, have had my boat 40+ years now; when I and my Spitfire / Harrier engineer dad saw the results at end of season with Metalshield as the boat was hoisted we both exclaimed " Wow ! " :encouragement:
 
Pavalijo said:
Each year I power wire-brush off the rust which affects maybe only 10% of the keel's surface area and then treat it with Fertan or similar. I have then used up to 5 coats of Primocon before antifouling.
After 5 or 6 months in the water the rust appears just as before.
I know that I need to do something more radical to get rid of the rust and am only trying to slow its development down, but someone told me that Primocon is not the product for that purpose - so what should I use?
Many thanks
Paul
Click to expand...

I use a couple of coats of Flag Rust Converter, which is more like a paint than Fertran is. Then use the primer (I prefer flag again, but Primocon is similar). On my previous boat the keels were quite bad, so I initially used several complete coats of the rust converter.
 
Wire brushing tends to drive rust into cast iron. Needle gunning does the same but even more so. Grit blasting is the most effective preparation method but not always convenient. An angle grinder does a reasonable job and does not drive rust into the metal.
 
My view is that once you have mechanical treated the iron/steel use hydrochloric acid followed by phosphoric acid before painting with you chosen coating.

Grit blasting is the best to get rid of the rust and roughen the surface for better paint adhesion.
 
Ruffles said:
I use an angle grinder with a flap disk. Aggressive enough to get back to bright metal.
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Might look very good, but if you warm it up and put on some phosphoric acid you'll see it popping and fizzing as it reacts with the rust left in the pores.

My view is that once you have mechanical treated the iron/steel use hydrochloric acid followed by phosphoric acid before painting with you chosen coating.
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:encouragement:
 
Seajet said:
The treatment which stands head and shoulders above the rest is

Dulux Metalshield

I know ' Dulux ' sounds like a joke but this is seriously good stuff, the keel looks almost as good on autumn lift out as when she is launched.

It's one part paint but requires the special Metalshield primer.

Best applied on bare metal as it can pickle other paint.

Available from places like Brewers - no connection apart from happy keel owner.
Click to expand...

+ 1 for this, works well, I treated rust first with phosphoric acid, cheaper than 'specialist' products at £10 for a thimble full.
 
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