rusty steel hulls

stiletto28 · 10-25-2010, 03:50 PM

Hello All,

Right, so we've just bought a 40' steel schooner. There are some rust issues on the exterior of the hull that we're going to have sandblasted, but what about the inside? There are some spot issues within the bilge, etc., and we're trying to decide as to the best method for rust removal...disc grinder? chemical? sandblast? Any thoughts on this would be useful, as we can't seem to agree on the best method....thanks!!

travler · 10-25-2010, 04:33 PM

i would invest in a couple of good needle guns and a lot of labor

NYCAP123 · 10-25-2010, 04:38 PM

Welcome to YF Stiletto28. It all depends how much area you need to work and its accessability. I also assume you done or plan to do a radiogauge to check the plate thickness. Search the files here. Much has been discussed.

Here's one link:
http://www.yachtforums.com/forums/st...=removing+rust

stiletto28 · 10-26-2010, 12:59 AM

Thanks for the input guys. We have had a survey done, and she's pretty solid throughout, ranging from 6-8mm for the majority and almost 16mm in the keel and rudder. I'll have a browse through that link, thanks again!

m2m · 10-26-2010, 09:24 AM

If the rust isn't to bad Tavler is right, invest in a needle gun and a wire brush. Clean the areas as best you can and follow with Ospho or something like Corroseal which converts the rust and seals the metal from further corrosion. This can be followed up with an epoxy paint system. Years ago I did this on a Army Corps Engineers boat in a machinery space and I saw the boat several years later and it still looked good.

sunshine08720 · 10-26-2010, 11:33 AM

You might want to take a look at C . I. M. (Chevrons Industrial Membrane) a liquid rubber membrane for the interior. Properly applied, it's there forever.

Loren Schweizer · 10-26-2010, 01:52 PM

Stiletto, immediately after sandblasting/needle gun/whatever, down to what they call "white metal"....add a coat or two of zinc primer.

Marmot · 10-26-2010, 03:02 PM

Quote:

Originally Posted by Loren Schweizer

Stiletto, immediately after sandblasting/needle gun/whatever, down to what they call "white metal"....add a coat or two of zinc primer.

Before doing anything of the sort I would determine what coating system I want to use and follow the procedures prescribed by the manufacturer of that coating.

Adding a layer of something that may or may not be compatible just leads to a duplication of work and expense, or a failure of the coating system in the near future.

sunshine08720 · 10-26-2010, 04:29 PM

For forty years I (my company) sandblasted and painted steel water tanks. We came across the Chevron product many years ago with a great degree of success, again give proper surface preparation and application. see
www.cimindustries.com

travler · 10-26-2010, 04:46 PM

a lot of good advice here as an owner of a steel boat for the last 40 years are so i would evaluate wich coating system i was going to use (as marmot sujested) and go for there we have used the ppg amerlock system for a few years now and have had good luck , there are other systems that are quite good i would evaluate wich would be best for your need,s

just a thought travler

Loren Schweizer · 10-27-2010, 12:26 PM

Quote:

Originally Posted by Marmot

Before doing anything of the sort I would determine what coating system I want to use and follow the procedures prescribed by the manufacturer of that coating.

Adding a layer of something that may or may not be compatible just leads to a duplication of work and expense, or a failure of the coating system in the near future.

Marmot, unlike many here who 'shoot from the lip', I have personal experience in building and maintaining A36 steel-plated expedition vessels. As advised by Joe Purtell of U.S. Paints/Azko Nobel, inorganic zinc primer on white metal finish is/was the default and initial coating in the process, followed by brand name (Interlux or Awlgrip) epoxy primers, then layers of fairing material and finishing with a brand name linear polyurethane.

At least that's how it was done, per the experts. Did some other coating--incompatible with zinc-- come on-market in the past couple of years that puts egg on my face?

I am by no means an expert and would hope that one weighs in on this.

Marmot · 10-27-2010, 01:23 PM

Quote:

Originally Posted by Loren Schweizer

Did some other coating--incompatible with zinc-- come on-market in the past couple of years that puts egg on my face?

Not that I know of. It is just good practice to select a coating system and prepare in accordance with that manufacturer's instructions before using any third party product that will underly that system.

No offense intended, it is just that there are many "zinc primers" on the market. Some of which may or may not use a carrier or solvent compatible with all coating systems.

Given the cost of hull preparation and application of a marine coating system it is simply a prudent approach to carefully plan such a project.

Henning · 10-27-2010, 01:31 PM

Inside, especially in an engineroom, I prefer CO2 blasting.

m2m · 10-27-2010, 02:08 PM

In another life I painted a lot of steel boats and the zinc primers were compatible with any epoxy topcoat. But I agree with Marmot it is unwise to mix different manufacturers products it's set up for failure or beter yet if there is a warranty issue your out of luck.

stiletto28 · 10-27-2010, 02:36 PM

Quote:

Originally Posted by Henning

Inside, especially in an engineroom, I prefer CO2 blasting.

Lots of great input here guys. We've ruled out sandblasting the interior, as it would be an epic mess to deal with.

However there is one bit that I'm not familiar with...CO2 blasting? I don't know much about steel boats as it is, so a bit of elaboration on this method would be awesome...We're heading down to the boat this weekend to fully assess how much rust-removal needs to be done on the interior, so more to follow.....cheers and many thanks