Steel Hull Repair

BJP_1

New member
Joined
21 Nov 2020
Messages
1
Visit site
HI All,

I'm looking at the best ways to remedy the rusty areas on my steel hulled yacht.

As far as I can tell there are two ways to do this.

The first and cheapest way seems to be to use an angle grinder with a steel wire brush attachment to grind away the problem areas and then prime and repaint.

The second and more expensive is to get the hull sand blasted.

I am on a tight budget so using the first approach seems to make the most sense to me.

I was wondering if anyone has any suggestions or past experience.

Thanks,

Joe
 

NormanS

Well-known member
Joined
10 Nov 2008
Messages
9,398
Visit site
I'm sure you're on the right lines there. Is the rust inside or outside? If inside, practically impossible to sand blast, and if outside, it's not worth it unless the whole hull needs to be done, so you're back to the electric wire brush.
Don't know where you are, but if outside in the UK, this is not a good time to expose bare steel to the weather. You want dry air, and as soon as an area is prepared, slap the primer on.
You'll probably get more, but not necessarily better, advice on the PBO forum.
 

Whitlock

Active member
Joined
17 Nov 2020
Messages
553
Visit site
If the rust is severe enough to require a wheel I would suggest that you have a hull survey to check that there is still sufficient thickness of steel there.
Going at it with a wheel will get the rust off but, depending on the age of the boat, it's comforting to know that you're not grinding too much away.
My boat is steel 10mm thickness below the waterline and only 14 years old but I took the opportunity this year to have an ultrasound survey while it was out of the water to prove that it was all OK, which it was. A friend, on the other hand, was digging out rust inside the anchor locker of his steel boat and went right through the hull.
 

srm

Well-known member
Joined
16 May 2004
Messages
2,701
Location
Azores, Terceira.
Visit site
There is a saying that steel hulls rust away from the inside. My experience confirms this; most of the exterior epoxy coating looked good after over ten years hard use however I eventually managed to sell the boat for its scrap value. The buyer stripped the interior to the bare hull and replated all suspect areas then shot blasted and painted inside and out!

I was advised by a competent surveyor (sadly they seem to be a minority in the trade these days) that cleaning and recoating the visible rusty patches is not effective as corrosion is probably going on under the old coatings. Each year you will be finding more places to clean and paint.

As suggested above power wire brush, or better a needle gun, and primer as a temporary holding treatment, but if you want to keep the boat full grit blasting and appropriate coatings in a dry environment is the only effective way - but its going to be expensive.

Incidentally, a wire brush in an angle grinder is not all that effective at removing rust, it tends to burnish giving a dark surface. I used a coarse abrasive sanding disk as that could shift paint and rust to get down to bright metal. But, be careful how much metal you remove!
 

Wansworth

Well-known member
Joined
8 May 2003
Messages
29,961
Location
SPAIN,Galicia
Visit site
Working on rusty old Dutch coasters a pen knife was always useful in attacking a bit of rust or flaking paint,a sort of therapy,anyway kept a brush with red primer handy and so we kept on top of the “rust”?
 

saab96

Active member
Joined
21 Feb 2009
Messages
181
Location
Bath, Somerset or sailing Portugal to Azores
www.lesweatheritt.com
Don’t use a steel wire brush. It deposits rust. Actually, don’t us a wire brush at all. Needle gun is better and you can do good localised diy sandblasting with a pistol attached to a bottle of compressed air. Worth investing because rust never sleeps. You have to get down to shiny metal no matter how much surface steel you remove. Remember that rust expands. It takes very little steel to make a frighteningly large pile of rust. If you go too far and are worried about pin holes or bigger holes, move to Plan B. Cut out and weld new plate. So get yourself a little welding machine to go with the needle gun. If you employ a welder to do the cutting, get it done by gas. An angle grinder will pepper the hull with rust seeds. Cheap and cheerful but not what you want.
 

38mess

Well-known member
Joined
9 Apr 2019
Messages
6,048
Location
All over the shop
Visit site
I took a job onboard an old steel coaster a while back, our days consisted of chipping hammer, needle gun, and chisels. All day we were at it. The Somali bosun said we were putting lipstick on a pig. The welder was busy patching the inside of the engine room to keep the sea out.
It was a happy ship.
 

rogerthebodger

Well-known member
Joined
3 Nov 2001
Messages
12,368
Visit site
I have a steel hull boat and use this process.

I grind paint away from rusty area and surround
Needle descale all the remaining loose rust.
Apply hydrochloric acid until you get clean gray metal (several applications may be necessary
Wash with lots of fresh water to remove the acid
Apply at least 2 coats of phosphoric acid (as used in most rust converters)
Apply at least 4 coats of Epoxy primer (I use high build primer to get a thick coating)
 

Lucy52

Active member
Joined
21 Dec 2014
Messages
592
Location
In the Mud, Conyer
Visit site
+one for the needle gun.

You can hire a needle gun and compressor, or an attachment to fit an SDS drill. They are also available to buy, try google, not cheap though.

A boat owner in the marina here used one to good effect, but it is quite noisy rattling a steel hull, it gave a very clean result.
 
Top