preparing and treatment to rusty keel

smeaks

smeaks

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lifted today and found the iron keel has surface corrosion, once the power washer (destroyer!) had done its job. So one more winter task to complete. What is the best method of preparing the keel for next season. My thoughts so far lie in the wire brush and sanding area followed by a primer and a two pac of something..... what products are best!

Also found the reason for a deteriation in engine performance, if the fisherman off amble wants what is left of his net ... get in touch!
 
I followed surveyors advice. Cleaned it up with a sanding flap wheel using an angle grinder, treated with rust converter (I used Vactan) then two coats of underwater primer then antifoul.

Should keep the rust at bay for a few years. Having it epoxied would be a longer fix but a lot more expensive.
 
We had exactly the same issue with our keel when it was lifted and we took the same course of action that you propose. The result was that small rust spots were appearing through the two coats of epoxy primer within the week. I wish that I had seen this thread from the WOA site regarding Jenoseel.... WOA Forum
 
G'day Steve,

If the keel is cast iron it will rust in seconds (Flash rusting) so you need to prep very small areas and get a coating on them before exposing more.

Sand blasting is by far the best method of cleaning and follow the nozzle with a coating on a long handled brush.

Cast iron is porous so many defects will be missed by sanding or grinding, so a coat of epoxy will help.

Hope this helps.

Avagoodweekend......
 
I have tried to remove rust and then keep it at bay over the last 50 years and on boats and cars with varying success!!

There is much to be said for an absolute removal of all rust followed by a very prompt application of epoxy.

The other option may be to remove the obvious and loose rust and apply a rust converter. in this way any rust in pits should be converted. I did hear of a practice where surfaces were wetted and allowed to develope surface rust and the rust converter used followed by primer etc.
I just keep on top of mine by chipping off the bad bits, wire brushing those areas, using a converter, priming and painting those bits and then giving the whole lot another coat. if I do this every year there is very little to do each time.
Good luck!!
 
You've really got 2 options. A thorough (and expensive) job that should last several years or a quick cheap job that will mean you repeat every year.
The thorough job is to abrasive blast and coat with a good quality anticorrosive. You need to get the anticorrosive on quickly after blasting but not, as someone has suggested, while blasting as you will just get blasting grit and corrosion debris in the coating and cause it to break down prematurely.

Quick route is to grind back to clean iron and coat with anticorrosive. Wire brushing and sanding is a very poor option as it does not clean corrosion off the surface. It will polish the rust and make it look shiny - but not remove it.

As someone in the marine coatings business I would urge you not to use a rust converter as it will compromise the performance of the anticorrosive coating. They are a short term fix but stop a good anticorrosive scheme from working effectively longer term.

Whatever coating you apply getting a good total film thickness will be important. Once you have that film apply antifouling as the last stage before relaunch.
 
For cleaning the keels no one has mentioned the Perago disk

http://www.paint-stripper.co.uk/perago.htm

not cheap but I was very surprised how effective it was on my keels and unlike an angle grinder there were almost no sparks though my coating of Davids zinc paint was not so good but I will clean them off next season and try something different.
I have no connection with this company.
pete
 
The Perago wheel looks interesting.
For large metal structures where abrasive blasting is not possible we often use a needle gun. A series of small metal rods that hit the surface to remove attached debris. Not normally practical for a private user but this could be a viable alternative. Not sure I would want to use it on wood or GRP though.
 
Points to ponder.

Cleaning rust from cast iron:

Grinding and sanding will not remove contaminants or material in the many flaws found in porous cast iron. the rotary action just spreads impurities; a grinding wheel will bur over pin holes and leave the rust and moisture trapped under a very thin layer of contaminated and heated cast.

Needle guns do the same thing by driving rust and contamination into holes so sanding, grinding and pounding are not recommended for long term good results.

Grit blasting means clean particles hit the surface and carry the contamination and rust away as more clean grit flows behind it. Cast iron keels should be grit blasted to class 2.5, that's all one colour with no shading or shadows visible.

Cast iron will flash rust so it's important to exclude oxygen and moisture within minutes, the less time it's left exposed the longer the it will last.

When we have blasted keels we use a full tent with fan and filters on the air exit and only work with the clean incoming air at our backs, this means all blasting dust and contamination is moving away from us and the keel, so the first coat of epoxy is applied above and behind the blasting nozzle as we go, ensuring a minimum exposure.

A second and sometimes a third coat or resin is applied wet on tacky to avoid sanding, taking extra time to work the resin well into any obvious porous areas.

The keel is then left for 24 hours to cure the epoxy. Then washed with fresh water and scrubbed to remove residue left by the curing process, the water will no longer form beads when its clean; after drying it is sanded with a 200 grit on a 3 foot length of 3 ply, just enough to remove the high gloss on the high spots, then any low areas (no sanding marks) are marked and filled with epoxy resin and micro balloons, next the whole keel is covered with a thin mix of micro balloons and epoxy resin using an 80mm paint roller with a 10mm nap. This is left to cure for 24 hours and washes as above.

Time for the 3 ply again (also known as a torture board) but with a 100 grit, then fill any remaining lows and if needed and do the leave it, wash it and sand it all over again. Or, if you got it right the first time, just take the gloss off and apply at least 2 or 3 more coats of resin, roll on and tip off with a long haired 2 or 3 inch brush.

Let it cure, wash it sand it, now apply a mist coat of epoxy primer, it will be touch dry in a matter of minutes then apply a full coat and let it cure, then lightly sand with a 100 grit and you are ready to apply some protection.

It's at this point you have to make the decision about what you are going to have under your antifoul, some use 2 pot paints, some use sealers, I have used the same stuff you see on the piles in the harbour holding up the jetty with some good results; I like a hard and thick coating to avoid and substrate damage when cleaning off old anti fouling down the track.

I hope this helps.

Avagoodweekend.
 
Last year I receive procedure from HEMPEL.
On the clean ( sanded) area : Light primer dissolved 15 %
3 layers HIGH PROTECT ( epoxy)
Than 1 layer undissolved Light primer
Antifouling
Expensive but good.
 
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