Rust on steel boats

[emcgovern]

Hi all,
New to forum and new to boating. Bought a 33' Dutch steel cruiser last October. Good condition but has a section of handrail that was scraped to the metal on the way down the Shannon to current marina in Lough Derg. I also notice spots of rust coming through here and there after the winter.

Three questions (probably covered umpteen times before but new to me):

1. How best to prepare the handrail metal before painting (steel brush?, sander??, angle grinder???)

2. How best to paint section of handrail. I have so far got four different answers -
a) clean to metal and apply four coats of International primer, as per tin, followed by top coat.
b) use Lowe rust primer instead of International primer.
c) use "red lead"(?) instead of a) or b)
d) use Owetrol(??) instead of a) or b) or c)

3. How best to deal with small individual spots of rust (down to metal with a screwdriver and as in 2. above??)

Apologies if this is overlong. Replies to some or all would be much appreciated as I want to do something soon and want to do it right!

Best regards

 

[ianabc]

Building a steel sailboat ...almost completed (6 years) ...6 months to go...
I believe that sandblasting the offending rust down to white metal is the only sure way to eliminate the rust.

We have used a small sandblaster gun for this.
It's a portable plastic can for the sand (or black grit which is less toxic) and a ceramic nozzle in steel wand connected with a hoswe to the sand container. These are often available from car repair shops, and are inexpensive. They require a small compressor of say 4 hp or more to power them.

We use a rental compressor that is moved with one wheel, wheelbarrow style. Petrol or electric probably available for rent.

Zinc primer but not the junk used to spray on cars which actually absorbs moisture! But paint with 70 or 80 percent zinc, which is quite expensive works well as the zinc protects the steel by sacrificing the zinc first as in galvanizing.

International makes a zinc rich metal primer but we have found others too. We have found zinc primer that has passed the 1,000 hour salt water spray test.

Sandlblasting requires deaf neighbors, a carbon mask with a felt prefilter, eye and ear protectoion from the sound of the compressor.

A horrible job really but with only a handrail you may be smiling in a few minutes!

We have seen people use a grinder and abrasive disk to clean off an entire hull....but only sandblasting to white metal really works!

 

[Jim_H]

Hi

Speaking as someone who bought a very secondhand steel cruiser I have discovered a few basic truths.

1) The only way to stop rust coming back is to get rid of it COMPLETELY. If there is any rust AT ALL in the bottom of a scratch IT WILL COME BACK !

2) The paint system is secondary to the above truth.

As regards 1 above, sandpaper/emery cloth are useless - do not waste your money.

You can buy abrasive discs for angle grinders, not the hard grinding discs but thick discs like an industrial scouring pad (from Screwfix). These are good for slight surface rust.

Gritblasting (sand is not very effective) is good but the initial outlay is high and it is very messy. For work on the hull this is the only option and apart from the 'spotting' guns used by the car trade you need decent sized compressors 10 - 12 cuft/min minimum.

There is a product from Hammerite, a billious green jelly, which comes in a small pot and claims to convert rust to shiny metal. IT DOES ... it really works !!!. BUT.... it does not work in the one or two applications that the lable claims. but over 3, 4, 5... applications with wire brushing it will do the job.

This may be just the thing for your handrail, it will take most of a day (in 15 min sessions with 30 min tea/ chat breaks) and you cannot do it afloat because the air over the water is so damp that the patch will be rusty in the 30 seconds that it takes to put the paint on. You may not be able to see it but it will be there !

As to paint.... there are many opinions, two pack epoxy- very good, but practice first at home because it's almost impossible to correct poor finish or poor application. It's also messy and tedious in small quantities.

Hammerite is surprisingly good. Its very, very tough when its dried (takes about 4 days to cure properly ... believe what they say on the tin about re-coating) and salt/UV resistance seems very good, but the finish is not always brilliant when applied outdoors.

Welcome to the world of steel boating .... The real advantage is that the tupperware stuff scuttles out of the way when you approach !!

Wood rots, GRP osmotes, steel rusts, plastic degrades. I KNOW.... lets make some LEAD boats. No corrosion, no degredation, 50 million year half life, easy to work and recycle. WHAT A MATERIAL !!!

 

[boatmike]

I would add that all these processes especially blasting clean down to base metal and promote new rust if not overcoated very quickly afterwards.

 

[cass123]

Also have a Dutch built steel cruiser.

Just a quick reaction on handrails - I simply use Hamerite.
Very simple as long as loose scale is first removed. After 2 weeks
it hardens out and after (in my case) 2 years still looks good.

 

[PaulJ]

As I understand it you are only talking of repairing/patching up relatively small areas so although Ian is quite right about sand blasting, it is a bit of a performance if you don't happen to own a sandblaster and have never done it before...... For small areas I have found an angle grinder is quite satisfactory and a lot easier. Ian is also right that you need to get down to clean metal but of course with an angle grinder it is easy to go too far so you need to be careful. A worn disc with nice round edges is needed. The abrasive discs mentioned by Jim sound like just the job but I have never used them.....

As for what you put on there afterwards, I guess it depends what is already on there. I have used Jotun Epoxy and can't speak highly enough of it. It is easy to use, tolerant of ambient conditions and very durable. Straight onto the bare metal you put "Jotamastic 87 Aluminium" which is a silver/grey epoxy primer. It is very thick so though you can brush it on, you will get brush marks but because it is so thick you can sand it back quite easily. The next coat is just "Jotamastic 87" which is made in a wide variety of colours and is a bit thinner than the first coat and can be brushed or rolled on. Those two coats will probably be enough and you can paint your topcoat straight onto the Jotamastic which is why it is made in so many colours as it doubles as an undercoat.

How Jotamastic will bond around the edges to other "ordinary" (non-epoxy) systems I wouldn't like to say but my guess is that, with proper cleaning up and preparation, it will be as good as anything else.

 

[emcgovern]

Thanks a million for the replies and sharing your experiences - plenty of good hints and plenty of food for thought. The bottom line is get down to clean metal first and take it from there - although I don't like the bit about having 30 seconds to get the paint on, if over water, before the dreaded "R" word returns.

Anyhow, will let you know how I get on and enjoy the coming season.