Best paint for a rusty keel?

[ash2020]

Hi all. We have a Varne 27 fin keel and the iron keel is showing quite a bit of rusting now. I am planning to scrape back the bad areas to bare metal but what would suggestions be for a good coating, before the antifoul goes on. Sadly, I haven't got time to strip the whole keel due to impending launch date, so it'll have to be the worst bits this time and then maybe a proper job next year.
Thanks.
Andrew

 

[Capt Popeye]

Heard that PRIMACON is very good, but not had experience of using it

 

[ash2020]

Thank you, I'll investigate.

 

[ashtead]

Common problem with Bavaria keels - every year I used to scrap back and apply Fertan to worst spots plus primer and anti fouling. Sadly every year the rust came back but it kept it at bay. I used a sandvik scraper with orange handle to scrap away rust as thought a cup brush on a drill was rather noisy/messy in case of use.

 

[Bilgediver]

Heard that PRIMACON is very good, but not had experience of using it

Nothing better but best if get to bare steel and apply ASAP. I apply at least two coats then antifoul on bare steel. One thing I have been doing for years is rather than just applying Primocon over cleaned up blemishes I have been putting a full coat on between antifouling every year following the coat over the blemishes. The keels were shot blasted around 1986 and are still good. Cast iron and Westerly Chieftain.

 

[rogerthebodger]

To me the best is to grit blast to gray metal then paint with epoxy tar with in 8 hours.

This is how I did my steel boat 10 year ago with not rust at last antifoul late last year.

Next best is needle descale/ chip and wire brush then remove rust with Hydrochloric acid followed by phosphoric acid then wash dry and paint with epoxy tar.

 

[Tranona]

Instead of Primocon suggest you use Jotun Vinygard. Same sort of primer but half the price - although you have to buy 5l. However, unless you get back t o bright metal using a grinder, flap wheel or needle gun nothing will stay on for long. In my experience using expensive Fertan to try and kill the rust left after just scraping is a waste of time. Whatever you do patching will only be temporary and you find you will be doing some more the next year. For many this is just part of the annual maintenance routine. The only long term solution is blasting and immediately applying epoxy. Does not need to be too expensive. I had my keel blasted last year and the total cost including all materials - Hempadur epoxy and Coppercoat was less than £600. Roughly 2 weeks in the middle of last summer, 3 days for blasting and epoxy, one day for Coppercoat and a week for cure before launching. lifted out on Tuesday after 9 months and all still firmly attached. Before and after pics attached.

 

[ianj99]

I use Rustbusters Epoxy <Mastic and FE123. I had the hull (steel) wet bead blasted in 2015 and then treated with FE123 where necessary and then 2 coats of Epoxy Mastic. So far no rusty spots.
I also did some blistered spots on the side decks with the same regime and 10years on, no issues.

The E Mastic is very viscous and does not run off edges and bumps like thinner epoxies.

Rust Remover & Prevention Treatments, Rust Proofing Cars | Rustbuster

 

[johnalison]

I used to get rust patches on our Sadler 29 and eventually got fed up with the yearly grind. Painting with Primocon never seemed to have any effect. Eventually, I used Hammerite as a primer and almost cured the rusting overnight. I believe that Hammerite is no longer the same stuff, but I would strongly recommend using a modern rust treatment rather than rely just on a primer such as Primocon, however clean you get it. I have had a lead keel for the last 20 yrs, and am not up to date with current treatments.

 

[ianj99]

The FE123 - also sold as Aquasteel, forms a skin once it has converted the rust so is not to be washed off. Above the waterline you can just leave it unpainted for months. The other rust converters seem to be a dilute version and not as durable.
Primocon is very thin and needs several coats, whereas the E-Mastic needs two at most, or one thick coat applied with a brush.

Jotun also do a version, called Jotamastic I think, which contains glass flakes. It gives a very glassy, tough finish, but is perhaps not as flexible as E=Mastic.

Jotamastic 90

 

[ashtead]

I just wondered if PBO had published any articles on topic of keel rust -maybe not much interest to owners of Hallberg and there Swedish friends but I had a recollection there might be something of interest ?

 

[rogerthebodger]

I just wondered if PBO had published any articles on topic of keel rust -maybe not much interest to owners of Hallberg and there Swedish friends but I had a recollection there might be something of interest ?

Mr Google will help

cast iron keel rust treatment - Google Search

 

[Quandary]

Anothe satisfied user of Vinyguard 88 from SML coatings, 5 litre tin and apply at least five coats, you can get 2-3 coats on per day, goes on in any weather unlike epoxy, better and cheaper than Primocon keeps well and is a good primer for metal cradles, gates or even woodwork so the big tin is never wasted. Gael force sell a version in 2.5 litre tins but it is not half as effective. Each year touch up any rusty spots on the bottom or the hull joint in the same way. Unless you have a lot of throw away brushes you need to buy some thinners as well (no. 7) though Int. No 3 antifouling thinners sems to be the same stuff.
Makes a good barrier primer between epoxy and a.f. if you choose to go that way.

 

[ashtead]

Almost too much info on Mr Google - I was just thinking some forumites might be tempted to pen a useful article on topic for PBO but that one might already exist ?

 

[ianj99]

Anothe satisfied user of Vinyguard 88 from SML coatings, 5 litre tin and apply at least five coats, you can get 2-3 coats on per day, goes on in any weather unlike epoxy, better and cheaper than Primocon keeps well and is a good primer for metal cradles, gates or even woodwork so the big tin is never wasted. Gael force sell a version in 2.5 litre tins but it is not half as effective. Each year touch up any rusty spots on the bottom or the hull joint in the same way. Unless you have a lot of throw away brushes you need to buy some thinners as well (no. 7) though Int. No 3 antifouling thinners sems to be the same stuff.
Makes a good barrier primer between epoxy and a.f. if you choose to go that way.

I've used Vinyguard as a tie coat and old AF sealer and it was like spreading margarine - viscous but easy to brush out and no drips.
But I prefer epoxy on bare metal because its one coat which matters when you have a 36' long keel steel ketch and are no spring chicken

However, FE123 where there are orange rusty spots and then a couple of coats of Vinyguard would probably as good as epoxy where there is little risk of mechanical damage.

 

[Aeolus]

I wire brush the worst of the rust and then use 1 coat of Vactan rust converter (available on ebay) and then one coat of Teamac metaclor primer and then 2 coats of antifoul over that. Lasts 2 years in the water and over the years there's been less and less rust forming.

 

[ithet]

When I had rusty keels I rubbed down the worst spots then painted the whole keel with a couple of coats of Flag Rust Convertor before coats of underwater primer such as Promocon. Did the full job for two years running. Subsequent years I just sport treat areas with the rust converter followed by primer, smaller area needs treating each year.

 

[MystyBlue2]

I have 0 experience with steel boats and even less when it is submerged in salt water but the best I've found DIY for steel jobs without spending a fortune on sandblasting and professional re-coating is,

Sand back with PLENTY of flap disks on a grinder, Like i mean get ALOT of them,

Once all thick rust has been removed with flap disks use KRUST, its a liquid compound that soaks into the remaining rust and dissolves it and brings the work piece back to bare steel. Pretty sure there will be similar products to this aswell,

Wipe away all gunk and Krust with acetone and a rag until clean and dry and ensure it is 100% grease and dirt free.

Red oxide primer the whole job and do 2-3 thick coats, ive found this to be THE BEST metal primer for longevity and keeping rust at bay.

Once that is dry paint to your chosen colour with suitable underwater steel paints....i have no clue what they are though. (As red oxide is not everyone's taste).

Hope this helps and good luck ?