How should I protect my steel hull from rust?

[qwert]

Originally Posted by RaymondR

One of the things I learned from all those years of steel boat maintenance was that designing a steel boat with longitudinal stringers should be a gailable offense under any proper justice offence.

Quite right, when I bought my steel boat it was twenty years old, The majority of rust I found originated from stringers without limber holes. Eighty seven new limber holes later............
I also poured epoxy into the "shelves"formed by the stringers up to the edge or to the height of the new limber holes so water couldn't collect there.

[RaymondR]

Originally Posted by qwert

Quite right, when I bought my steel boat it was twenty years old, The majority of rust I found originated from stringers without limber holes. Eighty seven new limber holes later............
I also poured epoxy into the "shelves"formed by the stringers up to the edge or to the height of the new limber holes so water couldn't collect there.

I used a cement render of boiled linseed oil and white cement to do the same thing. Worked well.

[oceanshoretiga]

Thanks for a great thread and serious comments and ideas. I’ve had steel yachts for about 45 years. My apologies if I tell too much of a story but the narrative history of my experience may help others to think about aspects of their steel yachts (as have the posts in this thread for me).

Two aspects I’ll comment on initially. First, every anode puts out the same power and multiple anodes can actually lead to too much power and the paint blows off. Many years ago I had a cathodic specialist and since then have had one or two anodes, mostly two, but when I see paint problems I go back to one only. Never had any problems with the steel.

Second, I use an Australian penetrating product called Xtroll along with its GP primer. Instructions are don’t grind the steel to a shiny surface but if so, let it rust a bit overnight (damped). Apply the product until all the rust area is glossy, which is evidence that all the rust has been penetrated and neutralised. Then primers and your favourite top coat(s).

Acid products are fine for cleaning rust stains but, in my view, not much good for rust itself.

Most of my problems are on deck and stem from three issues. First, the original sandblasting and spray painting just couldn’t get into all the deck crevices, hence rust.
Second, the build period was just starting to use stainless fittings on deck and my boat has a few, but things like hand-rails are welded-on steel (hence the crevices).
Third, early in my ownership/ignorance I had some welding done (pushpit and pulpit attachments) and that work created rust crevices.

I might add that the original primer still appears with deep scratches.

Inside is 90% fine. I keep an eye on bilge areas and an area under the prop shaft. The shaft does not drip when stationary.

Now to some background if you are still reading. I’ve owned two steel yachts, the first being a big learning curve. The second I bought when about 3 years in the water and had sailed from the east coast of Australia to Fremantle in the west. This boat is a Herreshoff Nereia 11.3m, cutter rigged. About a dozen were built professionally in Sydney in the 1970s. I’ve had mine for 39 years and she is a fantastic sea boat. I’ve sailed Tiga to Indonesia and around Cape Leeuwin for a brief sail to Albany in the Southern Ocean (nothing dramatic, except speed over the ground).

You might have guessed that I’m very attached to this yacht and work hard to keep her looking good and being strong. When a few months ago my insurance company asked for a survey, I asked for a delay for 6 months. They asked for pictures and date the rigging was done. They gave me a year because Tiga looks well cared for.

Thanks again for the discussion and for being part of a special group of yachts.

Cheers, Jim

[s/v Jedi]

About zincs: it’s true that you can have too much as well as not enough. The best way to determine what is right is by using a silver chloride reference cell connected to a good multimeter.

Here is one from an online shop: https://boatzincs.com/categories/too...electrode.html

[Willymc61]

Ecospeed is the answer. Applied to bare steel, it will most likely last the life of the vessel. Hard , tough impermeable surface that is 100% non toxic. You can clean your bottom in the greenest of harbors or pristine bays with zero poisonous residues going to the bottom. Not a new product... it has been on the Disney ships since 2006, it is on the world's largest icebreaker. Current record for a commercial ship, going into the ice regularly is 18 years before first haulout. They touched up a few scratches and relaunched without applying a fresh coat. check out subind.net , then contact me for product data sheets, application guides and more. Willy, willymc61@gmail.com

[RaymondR]

Two places on deck where I had persistent problems were under winches and under the timber around the cockpit coaming.

I solved the under winch problem by making "gaskets" from 1 mm aluminium sheet and Sikaflexing them to the deck.

The under timber problem was caused by rust starting at the screw holes and working it's evil way outwards. I solved this by welding around the holes with SS rods, grinding the weld flat and rethreading the holes.

[Noahr]

Back in the day when I ran big commercial ships the crew used needle guns, Ospho (acid) to convert the rust, then red lead to prime, and then paint with enamel. I am sure there are more high-tech coating systems these days, but the old system worked. Two-part epoxies are probably the weapon of choice these days.

[keelbolt]

I'm surprised no one has mentioned coal tar epoxy. I've owned steel for over 20 years. I've tried everything mentioned here with various results. As has been mentioned, it's all about the prep. Sandblasting to white metal is the only truly effective method but not always possible or practical. It's becoming extremely difficult to find any "yacht" yard that will allow it. As mentioned, go to the commercial yards. They will mostly turn you down for numerous excuses, especially in the states but some will oblige. Once you have white metal, red read it if you can get it, otherwise a simple zinc primer seems to work well, then a minimum of two coats of coal tar will seal your steel for least 20 years. I use Tnemec. It's expensive and hard to get but the results are outstanding. Bottom paint over that below the water line and a good urethane topsides will make it right.

When sandblasting is not an option, go with advice of phosphoric acid. It's your next best shot.

Rust NEVER sleeps!

Good luck. If your treat her well, she will return the favor!

[Mick of 42]

Originally Posted by keelbolt

I'm surprised no one has mentioned coal tar epoxy. I've owned steel for over 20 years. I've tried everything mentioned here with various results. As has been mentioned, it's all about the prep. Sandblasting to white metal is the only truly effective method but not always possible or practical. It's becoming extremely difficult to find any "yacht" yard that will allow it. As mentioned, go to the commercial yards. They will mostly turn you down for numerous excuses, especially in the states but some will oblige. Once you have white metal, red read it if you can get it, otherwise a simple zinc primer seems to work well, then a minimum of two coats of coal tar will seal your steel for least 20 years. I use Tnemec. It's expensive and hard to get but the results are outstanding. Bottom paint over that below the water line and a good urethane topsides will make it right.

When sandblasting is not an option, go with advice of phosphoric acid. It's your next best shot.

Rust NEVER sleeps!

Good luck. If your treat her well, she will return the favor!

Thanks for your answer.
Coal tar epoxy has been suggested many times down thread.