Preparation of keel for anti-fouling

[lumphammer]

I have scraped back the bottom half of my iron keel to get rid of the rusty bits. I am going to treat it with one of the rust converter type products, but what can I do to reduce the amount of rusty spots next year?

Is there a water proof primer I should use. e.g. Hammerite metal primer?
Any suggestions gratefully considered.

 

[Skysail]

I have used Primocon with success, but it needs 5 or 6 coats to work well.

 

[johnalison]

You'll need Primocon to help A/F to adhere, but Hammerite can work well, especially for touching-up rusty spots. You only need to wire-brush before painting on and following with Primocon.

 

[Quandary]

Primocon is an underwater primer and a boat product that actually works, I have used the 5-6 coat protection system as above with sucess, life usually 5-10 years before recoating. It is tolerant of limited preparation and will adhere well to most things, it worked even better 20 years ago when it was full of bitumen but stained through white antifouling. Rust convertors and Hammerite will do no harm but I have limited success with both on porous cast iron, though they may be better on steel.
No harm in applying the other coatings as long as you finish off with enough Primocon.

 

[gasdave]

I used a couple of coats of Fertan (they say one is enough) on my cleaned, brushed, ground keels. Then 5 coats of Primaocon. Then antifoul.

Far too early to comment on longevity though

 

[prv]

Jotun Jotamastic is an epoxy primer used on steel ships. You can buy it in more yacht-like quantities (rather than 20 litre drums) from Shepherd Marine; I haven't bought Jotamastic from them, but their Jotun antifoul prices are cheaper than Blakes etc so the primers might be a good deal too.

When I was touching up parts of a ship a couple of weeks ago the bosun wanted four coats of Jotamastic and four of topcoat, but this might be excessive for a yacht.

Pete

 

[flyingscampi]

Search the forums as there have been plenty of previous threads.

Last year, I used Copon Hycote 152LV on my keel which is an industrial 2 part epoxy for ships ballast tanks etc. This was recommended and supplied by AMC - the Coppercoat people.

The Hycote was applied after a farrow blasting and there was no trace of rust returning after one season. Hopefully for many more..

The chap at AMC told me the retail treatments are weak compared to industrial coatings and that the rust converters are not very good to paint over.

http://www.parkerjames.co.uk/downloads/HYCOTE_152LV_PRODUCT_DATA.pdf

 

[ghostlymoron]

I used Hammerite primer No 1 last year with limited success. This year I'm going to wire brush, Primocon, anti-foul. Didn't realise you needed 5 coats of Primocon but it is fast drying.
Hammerite primer didn't take the antifoul very well but possibly I had not left it long enough to cure fully. I left it overnight.

 

[Quandary]

I used Hammerite primer No 1 last year with limited success. This year I'm going to wire brush, Primocon, anti-foul. Didn't realise you needed 5 coats of Primocon but it is fast drying.
Hammerite primer didn't take the antifoul very well but possibly I had not left it long enough to cure fully. I left it overnight.

Multiple coats are just to build up an effective barrier, same as when you apply 2 pack epoxy to grp. When I painted more hulls I used to know how many microns a coat is, but not any more, with underwater coatings the more the better. The more thinners you add the thinner the coating will be. You will probably get your five coats out of a one litre tin so you can imagine that that volume will not give massive thickness when the solvent has evaporated. It does dry quickly especially at the start, but the later coats will need a bit more time if they are not to drag.
Put your first coat of antifouling on the top coat of Primocon as soon as it goes off to get the best key.
Choose a nice dry day if possible with at least one pint between each coat, you'll need a lift home after.

 

[oldsaltoz]

Is your keel cast iron or steel?

I ask because the treatment for each differs so some of the advice above may be for the wrong material.

Ie, Cast iron is porous so will hold moisture, coating a wet keel will not work.

Also note: cast iron will flash rust, meaning the first coat must be applied as soon as possible, the sooner the better, cast starts to rust only minutes after cleaning.

Avoid any grinding action to clean cast iron, it only pushes contamination into the pin holes and will continue to corrode. Grit blasting to class 2.5 is the standard, it should look a clean grey with no shadows.

Steel plate can be ground but blasting is much better.

 

[ghostlymoron]

Is your keel cast iron or steel?

I ask because the treatment for each differs so some of the advice above may be for the wrong material.

Ie, Cast iron is porous so will hold moisture, coating a wet keel will not work.

Also note: cast iron will flash rust, meaning the first coat must be applied as soon as possible, the sooner the better, cast starts to rust only minutes after cleaning.

Avoid any grinding action to clean cast iron, it only pushes contamination into the pin holes and will continue to corrode. Grit blasting to class 2.5 is the standard, it should look a clean grey with no shadows.

Steel plate can be ground but blasting is much better.

I agree that blasting to SS 2.5 is the ideal but the cost is prohibitive so most people use flap wheel/knotted rotary wire brush/needle gun instead which is probably why the rust returns the following year. Having said that, I am going to use knotted wire brush this year and hope for the best.

 

[Pasarell]

Cleaning keel for painting

I'm sorry guys but what a load of rubbish, old wives tales and folklore has been spouted here.

Most metal keels are cast iron and that cannot be blasted to Sa2.5! Most blasting standards including Swedish are for steel and cannot be applied to cast iron.

If the metal is ferrous, whether that is cast iron or steel, blasting is the best method of cleaning. If blasting is not possible then next best is needle gun and then grinding. This applies to all ferrous metal.

As someone already said, cast iron is often porous due to pits and blow holes in the casting so it is important to get it dry. Just as important is getting rid of salts on/in the surface so it is important to wash with fresh water - several times.

All ferrous metal will flash rust, steel as well as cast iron, so important to get the first anticorrosive coat on ASAP. Don't do this, though, until the salts have been removed by washing with fresh water.

Flash rusting is not actually a big problem for most anticorrosives provided it is "clean" rust. In this case ginger rust is good and black rust bad. Ginger indicates a little rust caused by clean water but black indicates salt is still present. If the surface does ginger most anticorrosives can still be used but get rid of any powdery rust first with a wire brush.

Talking of wire brushes, this comes just above doing nothing in terms of quality of surface preparation. Wire brushes clean rust to a nice shiny surface without removing it so it is in perfect condition to continue rusting under you nice new coating.

Most retail anticorrosives are not low performance compared with anticorrosives used on ships. Shipping companies will use both high and low performance products according to circumstances in the same way that any of us can do. Some retail products are modified to account for the way DIY users can apply them, nothing else.

There are hundreds of products used in commercial applications. These comments that keep appearing about "this is what big ships use" are uninformed. International are the biggest supplier in the world to commercial ships. Hempel (Blakes) come second. Loads of others come soon behind including Jotun, Chugoku (Sea Jet), Ameron, Nippon and lots of others. Choose the product that you are comfortable with, gives the best value in your area, meets your H&S requirements or your application conditions best. Given equal surface preparation you won't notice much difference in performance between high performance products (usually epoxies), or between surface tolerant products (usually singel pack).

Avoid using rust converters whenever you can and if you do use them remove any residue before overcoating with your anticorrosive. They will affect adhesion of your anticorrosive and that is really important.

Hope this helps and I'll now duck to avoid those who I've offended, but since I'm at a ship coating conference in Tokyo I'm probably out of range at the moment anyway.

 

[ShepherdMarine]

largest paint companies in world

Just a minor correction on size of paint companies in your post (courtesy Coatings World). Here is a list of coatings companies with a turnover greater than $1 billion in 2009. Hempel (Blakes) are way down the list.

1. AkzoNobel N.V. (The Netherlands) $14.124 billion
2. PPG Industries (USA) $10.935 billion
3. Henkel (Germany) $9.849 billion
4. Sherwin-Williams (USA) $6.521 billion
5. DuPont (USA) $4.3 billion
6. BASF (Germany) $3.729 billion
7. RPM (USA) $3,643 billion
8. Valspar (USA) $3.168 billion
9. Sika (Switzerland) $2.356 billion
10. Kansai Paint (Japan) $2.299 billion
11. Nippon Paint (Japan) $2.276 billion
12. 3M (USA) $2.2 billion
13. Jotun (Norway) $1.87 billion
14. DAW (Germany) $1.471 billion
15. Masco (USA) $1.440 billion
16. Comex (Mexico) $1.400 billion
17. H.B. Fuller (USA) $1.391 billion
18. Hempel (Denmark) $1.347 billion
19. Beckers (Sweden) $1.316 billion
20. Asian Paints (India) $1.062 billion
21. Bredero Shaw (Canada) $1.053 billion
22. Chugoku Marine Paints (Japan) $1.036 billion