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Old 23-04-2006, 22:18   #1
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Rust never sleeps

Being new to a steel vessel and to working in metals generally I have a question for all you knowledgeable bods out there. We have just acquired a 44 ft steel Roberts with has some rust in the odd spot, surprising I know. My main concern is in the ribbing in the bilge areas. Could some one please tell us the best way to clean it, treat it, and protect it in the future. Also the aluminium mast is a bit pitted and we would like to clean that up as well. Then off we go on our adeventure. Thanks in anticipation, Enzwell
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Old 23-04-2006, 23:10   #2
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I've been a metalsmith for a long long long time now and there is only a couple ways to completely get rust off. Grind or sand blast. Nitric acid will work too but I never mentioned that, OK.

One can chip away the iron oxide and re-paint but it'll surely come back. Sand blasting is the best method. But if it's in a hard to get spot you may not get it all. Growth prevention would be the best for that. Once the metal is clean it's not hard to protect in non-abrasion areas. Epoxy based paints will coat the metal and protect it from moisture intrusion. The best thing out there is Belzona but that's for pumps and valves and one could not really afford to paint a whole boat in that stuff unless you're Bill Gates.

The object it to protect the metal before it starts the oxidation process. Once it's contaminated it's a lot of work trying to bring it back.

If you have rust between a rib and the skin, the best thing is to hammer on the skin just outside of the rib and break up the iron oxide. Once it's out you might be able to sand blast in there to get what you can and then seal it off with epoxy paint. The best thing you can do for the boat is keep the water out of the bilges. Heat and saltwater are the two best things for the growth of iron oxide.

As for your mast, it's probably serving as an anode. Just remember, "Nothing lasts forever".

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Old 24-04-2006, 01:21   #3
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there is another way...
Sandblasting is the best if you can but sometimes it just isn't possible. I own a 35 year old steel boat and I can now weld very well and know how to treat weathered steel. If it's a big job, you need an air compressor and a scaler and chisel. I found the tools in a cheap auto parts place. Get the big stuff with a air powered chisel then go after it with a needle gun (scaler) till you are certain you have it all, then do it again to get the stuff you thought you already got. Ear protection a must. I tried the rust converters (acids) with no luck. When the metal is truly exposed, even down in the pits and the rust scale is gone, then wire brush and flush with water which will leave an ogange film... thats OK. There are paints made for this. The one that is available in US is POR 15. In Australia Altex pre-prime 617 is the best. The paints are 'encapsulating' so are intended for a rough finish and will even tolerate the odd loose grain. When done (after following instructions carefully), you can begin the normal routine, one or two of normal primer then at least two of high build epoxy then at least two coats of top coat such as a nice catalised acrilic polyuerathane. On the mast and other aluminium bits... same thing has worked for me. I have saved some spars and hatch's with this. Use the same scalers and final wire brush then the pre prime paint. I only put a top coat on the pre-prime on the alloy. For small areas you can get away without the air tools but it takes time. I have a dead screw driver reserved for the odd repair. A shop vac is also a good accessory.

Get in the habit because a steel boat will need attention but they are so tough!

Cheers
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Old 24-04-2006, 01:25   #4
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There is also Phosphoric Acid, which is a little milder to use and changes the state of the Rust or Iron oxide to ??? forgot, something else though. Most Ferrouse metal etch primers use this acid. PA10 primer stands for Phosphoric Acid 10%. It is also used to clean concrete. Coca Cola has it in it by the way and is why copper coins desolve.
Another product I have had a great deal of good results with is made by "Plasitkote". It is a white liquid that comes in a black plastic squeezy bottle. When it dries, any rust turns into a hard black surface that can be painted over. It works very well and especially if you are going to paint single pot coatings over it. I have not tried two pot anythings over it yet, so I can't comment on whether two pots would hold. Basicaly you get rid of the worst flaky rust and then liberaly paint this stuff over the remaining metal.
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Old 24-04-2006, 01:47   #5
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Iron Oxide + Phosphoric Acid* = Iron Phosphate (Black Oxide or Hammerscale)
In products such as ‘Ospho’, ‘Naval Jelly’, ‘Rust-Lok’, etc.
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Old 24-04-2006, 13:06   #6
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That's the one. I kept having Iron Pyrite come to mind and new that wasn't it. Must be age ( I hope) but words seem to just disappear from my little head now. Very frustrating at times.
So anyway, if you plant the spuds to a depth of.......? no that's not it, what are we talking about???
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Old 24-04-2006, 13:51   #7
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y

POR 15 I have used this,good results,needs topcoat if UV rays present,harsh fumes when applying.Plasitkote,rust converter is real interesting,very friendly to use but does not like standing water on it.I have coated metal and left it outside in the elements and it will last for a couple of years.If any areas start to show you just brush it back over and you are good to go again.I like this stuff the best because no rust develops under the coat,because if it shows up, you will know and like some other coatings it can be rusting beneath it and you will never no untill it begins to peel.You can put this stuff on your hands,it is suppose to be non toxic.It goes under the name of Rustnot as well and is sold in NAPA automotive stores in America.With these products you need some rust on the metal for them to work.I have used both of these products first hand extensively and i would give the Rustnot the edge(ease of application) for any projects that were not going to be submerged constantly.BTW I have painted over Rustnot with a 2Part epoxy paint and it just pulled off the Rustnot and came off in huge pieces.I only did it once so i cannot say for sure what your result would be,i just do not do it anymore.I was left with a bare metal.My final advice is nothing is permanent and it is all about staying on top of your maintenance routine and it will outlast you.
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Old 24-04-2006, 19:36   #8
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POR 15

They make a metal ready product for use B4 applying the POR. The stuff works also as awater barrier and dries very smooth. I have painted the keel ( thre coats ) and the hull ( two coats ) and it is working well. When the anti fouling wears off the black POR is visible and is still smooth. I buff up with a socth brite pad and roll on some more VC17. Works for me.
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Old 25-04-2006, 20:10   #9
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Thanks all.

I will read all this and digest. Thanks for all your advice, I'm sure I will be back with more questions.
Enzwell
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Old 25-02-2007, 21:09   #10
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Anyone tried CorrosionX rust preventer? Corrosion Technologies Corporation I saw it at the Miami boat show. Of course the salesman claim it is the best thing since sliced bread. I was just wondering if CorrosionX or any other product is the magic elixer to prevent rust.
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Old 25-02-2007, 21:59   #11
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Like any other form of coating it is ALL about the prep. Mechanical or abrasive blasting is the ONLY way to ensure you have a suitable substrate. Get the priming coating on as soon as the prep is done. In your case localised mechanical cleaning may be the best option. Only acid wash if you can dry the area 100% immediately as you will end up with oxidation very quickly regardless what they say about a "protective coating". (20+ years looking after steel boats & ships)
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Old 25-02-2007, 22:50   #12
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Totally agree with previous....Preperation with the big P..that is abrasive cleaning till white metal or close. Have a look at the various military, comercial and paint manufacturers specifications. Its all blast to a specific finish. Then a high quality 2 part epoxy primer and high build top coats. For more information see The metal boat society, better still become a member......metalboatsociety.org ... cheers Martin
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Old 26-02-2007, 02:48   #13
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Progress wishlist...

As I work through my boat treating the steel and building the interior furniture I reflect on how I wish the boat should have been built.

Abrasive blasting is clearly the best method, followed by the application of a suitable quality paint system. However, while the exterior of a steel boat can be properly blasted the interior is far more difficult.

In practical terms I really wish that my previous builder had left cutouts in frames and stringers so that any water could drain away freely. Wherever water has been able to pool rust has formed. If it was salt water it was bad rust. Just goes straight through the paint. I spend my time drilling drain holes.

The second thing that I wish had been done is to use a thicker coating. My preference (if I had been building) would have been to use Sigmaweld as a primer, followed by two pack epoxy paint and two pack polyurethane. If different coloured paints were used it would be possible to determine the condition of the coating visually.

I would suspect that if the steel was treated with phosphoric acid and then primed before being welded that some of the abrasive blasting could be avoided. This could be of use in the interior where it is almost impossible to achieve a first class blast.

The third technique that I wish had been used is the extensive use of stainless steel (above the waterline and inside) where ever paint can be chipped or abraded, water can pool or anything needs to be attached to the boat.

And finally I wish that all frames and stringers had been predrilled for the mounting of interior furniture, and water lines and buttock marks had been left on the frames (just small grinder marks would have done).

These actions would have made a far better hull and made the overall process quicker and easier.
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