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Old 11-16-2012, 10:38 AM   #1
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Shintullah update/bottom treatment question

Well, Shintullah is on the hard starting her transformation, the bottom has been sandblasted. The yard is recommending they zinc chromate the bottom then coal tar, then bottom paint with high copper paint. Is this the standard way to treat a steel boat? Comments? Agree? Disagree?
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Old 11-16-2012, 10:54 AM   #2
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Talonewo,
Look at Interlux's website. Near the bottom it tells the recommended (by them) prep and coatings for all hull materials. I used this as a guide to put anti-foul on my aluminum skiff. It took three different kinds of paint/coatings and a total of about 14 coats total. And of course this was using their products.

I looked it up.
For steel and iron they recommend;
Vin-Lux Primwash 1 coat
Primer 4 coats
Antifouling 2-3 coats
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Old 11-16-2012, 11:17 AM   #3
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Please note Eric has quoted a system very different than you plan. Best you PM with Delfin on this Forum. He is a steel boat guy. Coal tar you say - hummmmm. Copper paint is unfortunately falling into enviro limbo. Where is this yard located? If not to late, take a deep breath and re-assess your options.
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Old 11-16-2012, 11:29 AM   #4
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Quote:
Originally Posted by Talonewo View Post
Well, Shintullah is on the hard starting her transformation, the bottom has been sandblasted. The yard is recommending they zinc chromate the bottom then coal tar, then bottom paint with high copper paint. Is this the standard way to treat a steel boat? Comments? Agree? Disagree?
I would prefer an epoxy barrier coat rather than coal tar, especially if the coal tar does not dry hard so the bottom paint has something to stick to. I usually use zinc primer on most metal things on the boat before painting. Besides it sort of looks like the ugly DD green.

What brand of high copper paint?
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Old 11-16-2012, 01:00 PM   #5
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A place I've found some good information for Steel & Aluminum Hulls

MetalBoatbuilding.org • Index page
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Old 11-16-2012, 09:27 PM   #6
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Quote:
Originally Posted by Talonewo View Post
Well, Shintullah is on the hard starting her transformation, the bottom has been sandblasted. The yard is recommending they zinc chromate the bottom then coal tar, then bottom paint with high copper paint. Is this the standard way to treat a steel boat? Comments? Agree? Disagree?
To do a steel bottom, the first coating should ideally be applied within a few hours of sandblasting the metal bright. I am not sure if the picture you show is, in the view of the yard, now paint ready but if so I would be a little nervous. It looks ready to apply paint that will be failing soon, but not for what you probably are looking for.

I'm going to re-do Delfin's bottom, probably next year, and I can only tell you what I intend to do. May not be the best and others may have other opinions (count on it), but this is what I will be doing, using AwlGrip's products, which are the only ones I know very well.

1. Sand blast to bright metal to a 2 mil profile
2. Coat within 4 hours (do by sections if necessary) with Max Cor CF. This is supposedly better than Zinc Chromate, which would not be a very high bar. Awlgrip used to make a killer product that isn't available in the U.S. anymore and I am hoping the Max Cor is as good.
3. 24 hours later, apply HullGard Extra Epoxy primer to 4 mils dry (2 coats).
4. no more than 24 hours later, apply HullGard Epoxy primer to 10 mills dry (probably 5 coats).
5. When the last coat of the primer is tack free, apply Awlstar Gold Label to 12 mils dry.

Re-coating a couple of years later can be whatever you want that is compatible with the Awlstar, or you can stick with that.

Except for renewing your bottom paint every couple of years, that should result in a very, very long lived substrate.

Hope that helps.
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Old 11-17-2012, 05:47 AM   #7
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I thought coal tar coatings were discontinued and not available anymore. They were great on commercial boats and barges, but I wasn't aware that they used this coating system on yachts. They certainly held up well.
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Old 11-18-2012, 04:28 AM   #8
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Sunchaser, the yard is in Slidell La, just north of New Orleans.
Phil Fill, the coal tar is an epoxy, the yard says they use “mostly Algrip products”. At this point I’m very pleased with this yard, communication has been a slight issue, it is not their fault, I’m in Afghanistan for the next four months, phone calls aren’t easy and the 12 hour time difference doesn’t help. Emailing is just not as good as a good face to face discussion.
Delfin, thanks that is exactly what I’m looking for. I will double check with the yard on why they recommend zinc chromate over the Max Cor CF, especially since they use Awlgrip materials. I will also ask to compare the HullGard Extra Epoxy primer to the coal tar.
Three weeks ago I did not know the difference between house paint and bottom paint. I have learned this topic is just like most… if you ask ten people you will get nine different answers. My research on the coal tar epoxy has been interesting. I see the primary goal of the below the waterline coating on a steel boat is corrosion control, secondary is anti growth protection. I researched this product on the marine engineering forums; in the discussions everyone agreed it is an excellent product for corrosion control the concerns were the health and safety aspect during the application process. If the oil companies engineers use it to protect their billion dollar structures from corrosion it should be ok for my boat. I liken this product selection to cars… if I pick a seven series BMW and you like the Mercedes so be it, we will just agree to disagree… I have no clue what I’m doing and want to make sure I don’t buy the yugo
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Old 11-18-2012, 06:07 AM   #9
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I have never heard of a steel boat bottom job that did not start with,

Sand blast the entire surface to "water white" and,,,,
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Old 11-18-2012, 10:05 AM   #10
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There are antifoulant bottom paints on the market that are compatible with metal hulls and running gear. They do not contain copper.

If I hat a metal boat, I would look into these coatings rather than copper and methods to isolate the copper from the hull.
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Old 11-18-2012, 10:08 AM   #11
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Quote:
Originally Posted by Talonewo View Post
.......... If the oil companies engineers use it to protect their billion dollar structures from corrosion it should be ok for my boat...........
Keep in mind that your boat is intended to move through the water and the oil company structures are not. That can make a difference.
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Old 11-18-2012, 10:58 AM   #12
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Coal tar epoxies are successfully used on steel boat hulls. Fairing can be an issue with coal tar epoxies, thus their preferred use is for hull interiors. But as noted by other posters, preparation is the key with bare metal required. Your photo shows poor preparation so far. If the yard puts the bottom protective "system" over that bottom, hull protection and life before redo are unknowns.

If your yard is into it, have them give you a price with "system" alternatives - and details for hull preparation.
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Old 11-18-2012, 11:09 AM   #13
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I would echo Sunchaser's comments. Unless you have already discussed it, you might ask for details on surface preparation, specifically the interval between sandblasting and the first coat. More than a few hours and you are painting over oxidation. In addition, grinding really doesn't do the job, it must be sandblasted if you want a long lasting subsurface on which you can maintain bottom paint. I wouldn't lead them to the right answer, just let them explain how they like to do this, naming the specific brands and formulations they'll use. If you're out of country, it would be good to have someone there on the day they prepare the hull for painting, as this is where your money will be spent, or possibly wasted.

I assume you aren't going to Afghanistan on vacation, so thank you for whatever it is you're doing there.
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Old 03-01-2013, 12:52 AM   #14
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This project moves forward slowly…. The prep is done the epoxy is on now it is time for the anti foul… the yard is asking what color I want… other than personal preference and esthetics what else should I consider when picking a color for the anti foul? The boats home waters are in Texas. My first thought is, the epoxy is black I was thinking of picking something other than black so I could see when the anti foul is gone…
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Old 03-01-2013, 05:43 AM   #15
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Some ocean going folks think white is less likely to have whale strikes.

My preference is for a paint that wears off.

So the first coat will be one color , and the rest of the coats will be the visible color.

Then its easy to see when more paint is required.

Remember paint of any type on top of epoxy usually has a very small window to be applied after the last epoxy coat is laid on. READ the instructions!!!

In many cases when the epoxy does not stick to your finger , but will show a fingerprint , its time for the first topcoat.
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Old 03-01-2013, 07:44 AM   #16
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Many copper based bottom paints are compatable with steel hulls (alumnum is a different story)....especially if there's a good epoxy barrier coat although that's not absolutely necessary for compatibility)....maybe not all bottom paints..but most..read ore here if uncertain

Antifouling Paint For Boats & Yachts | Interlux


Most paint the first coat a different color than the final to let tnem know when the paint is getting thin...if you wait till the epoxt shield...your fouling may get pretty bad quick.

As to colors...some fade above the waterline prett bad...white sometimes takes on a sickly green color untill the surface washes/is scrubbed off.

The traditional blue, black and red do OK...but look around and ask before you decide.
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Old 03-02-2013, 01:58 PM   #17
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I'll wade in too. My boat hull is a combination. The basic hull is fiberglass but there is a large fabricated steel keel and rudder that goes from the bow to the stern and tapers from a few inches to ~3 ft deep at the stern so I too have a big chunk to look after.

I had it done 15 years or more ago and it still is holding up well. Sandblasted to white. I saw it after it was done. Then the zinc coating was sprayed on, then epoxy sprayed, 2 coats, and then the bottom paint. The bottom paint is copper based, Amercoat.
My coatings were from Devoe Coatings, now International, and were basically what was commonly used on tugs, fishboats, etc. The yard I had it done at, alas now gone, knew what they were about as they did lots of commercial stuff also. I was peanuts although they didn't treat me as such.

At home I have the actual product names although that may now be of not much help as names and product formulations change. The zinc coat was Devoe Cathacote if memory serves., can't remember the epoxy and the bottom paint was Amercoat ABC ablative which I still use.

Of course zincs must be applied and new bottom paint also every two years.

The photos you showed show the prep hasn't been finished. There should be no old paint or rust residue.

Or does the photo show some fairing compounds?
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Old 03-02-2013, 04:01 PM   #18
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I go with Phil

Make an effort and choose a system with epoxy before the antifouling. Choose industrial coatings that have the same quality or better and are not priced as "marine coatings".

P
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Old 06-02-2013, 02:18 AM   #19
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The project moves forward slow but sure, I will be back in the states in a week or two can't wait to see it, should be in the spray booth in the next few weeks.
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Old 06-26-2013, 06:56 PM   #20
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Slow but sure the project moves forward, I'm back in the states and actually got to see my boat.
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