Dunking Bulkhead Door Posts in Primer

[JimC]

Galvanizing is cheap, its sandblasting that's expensive. I did 2 bulkheads, a chassis, 4 t-supports, and probably a hundred other parts for about 500 bucks. Blasting all that was more than 2k though.

If you are concerned about outside finish, the blast, galv, re-blast areas to be painted (to create a surface with excellent key) and then epoxy prime and paint as normal with car paint. Not house paint.

[kevkon]

How can you blast the insides of those channels?

[leafsprung]

if it did the boat guys could save a bundle on stainless

So make your bulkhead out of stainless . . .

the electrocoat primers are state of the art in corrosion resistance

E coat is a decades old process, so Im not sure what makes it state of the art. They were e-coating pinzgauers 40 years ago, and while better than some contemporaries, they still rust. Once the first stone comes off your tire and chips or scratches the ecoat, the coating is completely compromised. Galvanizing is far more resistant to rust spreading under the coating because it bonds to the steel. Even if it gets a scratch or scrape completely through the coating, rust will not spread under galvanizing. Hate to burst your bubble, but it is still better than e-coat.

[JackIIA]

Thanks all. This gives me abit more direction...and sounds like some more homework too

[JackIIA]

How can you blast the insides of those channels?

Well I media blasted the inside of my channels using glass bead, after making initial cuts in the posts during the rebuild stage. But the results were admittedly mixed. I found it was fine where you could get direct focus of the blasting gun, but not so great where you've got a bend in the metal or other obstacle and you're trying to work the gun up into a bulkhead recess.

[leafsprung]

acid dip instead of blasting

[Bud]

Another vote for acid dipping, the only way to go in my opinion. Galvanizing is a chemical reaction, not simply a coating. For the reaction to take place, the steel must be bare, and only acid dipping can accomplish this. A major reason for the use of galvanizing is to solve the problems on the inside of the bulkhead.

A stainless steel bulkhead would be great, but the back-purging of welds would be a nightmare during construction, likely preventing the use of such welding techniques. An absence of back-purging leads to contamination and the development of chromium carbides in the weld. The results of this are a loss of corrosion resistance as the chromium is no longer free to do it's job, and a loss in strength through micro-cracks via the chromium carbides. In the long term, this will lead to rusty and failed welds.

Painting a galvanized surface is easily accomplished, talk to your galvanizer about it.

With any choice, it's all about preparation and attention to subtleties.

For a thorough explanation on galvanizing:

http://www.gottdenerdesigns.com/galvanizing.html

Brett

[kevkon]

So make your bulkhead out of stainless . . .



E coat is a decades old process, so Im not sure what makes it state of the art. They were e-coating pinzgauers 40 years ago, and while better than some contemporaries, they still rust. Once the first stone comes off your tire and chips or scratches the ecoat, the coating is completely compromised. Galvanizing is far more resistant to rust spreading under the coating because it bonds to the steel. Even if it gets a scratch or scrape completely through the coating, rust will not spread under galvanizing. Hate to burst your bubble, but it is still better than e-coat.

I can't agree that modern electro coating and immersion baths are compromised by a single scratch. I would also point out that zinc plating is a sacrificial surface which fairs in relation to that which it is applied and the conditions it is exposed to.
Anyway, you are not bursting my bubble since I'm not e-coating anything nor am I dipping it in zinc. In this case both are unnecessary to keep a Series bulkhead corrosion free.

[JimCT]

back purging SS

Titanium yes, SS no. Marine welder and fabricator here and welding up a SS bulkhead would be fine, just not sure it would be worth the price. And epoxy paint systems out perform galvi now. Check what they use on oil rigs in a salt water environment and a big investment. Galvanizing used to be the only option, but those days are long gone. And I work with metals that are constantly exposed to salt water, so on LR the epoxy paint systems would work fine.

[thixon]

IMO, galvy is overkill unless you're in the northeast, and going to treat the truck like its a red headed step-child.

That being said, I understand the motivation to want to overprotect a part you can no longer replace. However, I enjoy the work, so if it rusts again, I'll just re-do it (in 20 or 30 years).

Are you going to treat the truck like a collector car? If so, you'll be fine with the blast, paint, internal wax recomendation. Think about how long it took for it to get to its present condition anyway.

If its gonna be a trail/mudder/winter driver in Maine then maybe you should think about the galvy option.

If you do dip it, it will take some extra prep work to get it ready for paint. Been there, done it.

Good luck with it.

[Momo]

I have a bulkhead out for repairs right now. It will get an acid dip and then be galvanized because it's the only way I can be sure that every void has been reached.

I live in a beach town and have worked aboard boats. I have never seen a common coating that holds up as well as galvanizing does. Frankly I think powdercoating sucks by comparison, at least for any heavy-duty use. Fine for a show car restoration, but not for a 4x4 that will get constant stone chips, submersion, mud splatter, abrasion, etc. Look at any 10 year old Disco bumper that has seen regular off road use, you'll see. Epoxy is great, but way more expensive than galvanizing and is still a coating.

The bottom line is, coatings peel, zinc plating oxidizes and thins. Which is worse?

Well, by the time you see evidence the coating's given way, the rust has usually taken hold pretty deeply. On the other hand, zinc thins out gradually, and when you finally see the orange streaks of iron oxide, you will still have an intact piece. Where we live, there is a playground right on the beach, perpetually wet, salt air environment, right? The coatings on the monkey bars are peeled and the steel is scarred and pitted. Some of the fittings on those same monkey bars are hot-dip galvanized, and they are crusty, but the zinc is doing just what it is supposed to do, function as a sacrificial plating. Underneath the zinc, the steel is undisturbed.

Another example is when Land Rover quit galvanizing the cappings on the 90/110. Those cappings rust away. That was never a problem on Series Land Rovers. Also, how many bulkheads have you seen that are full of rust, and yet their windscreen frames are still in good shape?

As far as prepping zinc for paint, well, good prep is always necessary, and never "cheap".

Finally, I challenge anyone to try to peel zinc off any piece of steel. Dollar for dollar, it is the best solution for this application.

[kevkon]

I definitely agree with you about the powder coating. I am seeing more and more examples of de-lamination with powder coated parts.
Just for the record, I agree that galvanizing is an effective and time proven method of corrosion protection. However, given the origin of this thread, I personally believe there are much better options available. But everyone has their preferences.

[Bud]

Stainless Steel Welding

JimCT,

I disagree with "titanium yes, SS no"; it is just not that simple in my eye. The back-purging (or use of SolarFlux) of stainless steel is an industry accepted practice for achieving "best results". It is a widely documented subject. I would agree that back-purging is not a required practice in all applications. For the potential price of a SS bulkhead, I would want back-purged welds.

http://www.gowelding.com/met/austenitic.html

I urge others interested in this subject to do their own research, and determine for themselves what is the best course of action for their potential applications.

[TedW]

IMO, galvy is overkill unless you're in the northeast

I can't speak for the rest of the country, but here in Maine there is no such thing as overkill when it comes to preventing rust.

My sled would dissolve in the garage if I didn't galvanize or Waxoyl bathe every inch of it.

IMO the galvy bulkhead (and breakfast, and steering box) is a swell idea. I say go nuts.

A few years ago the boys from Wise Owl / Rocky Mountain were working on doors with hot-dip galvanized frames, but were unhappy with their first batch and apparently dropped the idea - too bad, as I was (and am still) ready to buy a set if they ever figure it out. Combine those with their aluminium door tops and you'd have doors for life.

[ECR]

Just strip galvanize and be done with it. Mike's claims of longevity with epoxy primer is suspect IMO...

Our dunking of bulkheads was an attempt to get paint on the inside of the metal. Stripping and galvanizing a bulkhead would be far superior, but customers did not want that due to costs involved. So we came up with dunking them in a quality primer to help slow down rust. It was never a "no rust" claim, nor was it a claim that it was superior to galvanizing. It was a claim that some paint up in those areas has to help somewhat and it didn't add as much to the customers bill.
In no way do I think dunking something in primer is superior to galvanizing, otherwise we'd be dunking frames instead of galvanizing them... nutz.