Salt/Water Seal

[Stan Back]

I need some help.  After 6 years on the salt we are “refreshing” our roadster.  The biggest salt problem seems to be between the steel ‘29 body and the fabricated steel frame.  The fit is not perfect and rust has developed there.  We’re taking care of that as best we can, and would like to prevent it from happening so much in the future.

I’d like to find a foam (closed-cell, open-cell?) strip or like product that would seal out the water.  The gap is from near zero to 1/8th or 1/4 of an inch or so, so something that would compress and conform would be ideal.

The dainty frame rails are about 5” wide.  Would weatherstripping products work, or would these soak in the water?  The stock-type body welting(?) is like an old army belt and I think would just act like a wick.

Any good ideas out there?  Jack?  Kent?  Tom?

[Dean Los Angeles]

Rust is a form of corrosion. The oxygen in the water is a corrosive agent. The salt with the water forms an electrolyte and accelerates the process.

Your chances of sealing them out versus sealing them in is pretty slim. Protecting the base metal is the best choice with a properly prepared surface and paint, preferably epoxy.

If you are going to completely disassemble the frame, then powder coat is a good option. If you can, double powder coat using a zinc rich primer.

Salt and water isn't the only thing to look at. The typical vehicle has many different metals. Galvanic corrosion might also be happening. The different metals react with the salt water electrolyte to form a battery. Ships counteract these forces by installing a metal that corrodes easier than the base metal. Either zinc or magnesium works as a sacrificial anode.

Alternative: Gold plate the whole works.

[JackD]

After you have cleaned and protected the metal by whatever method suits you, pour a re-enterable, flexable mix into the space , simular to the material used in the seams between the boards on a wooden boat.
 deck.
For door slammers with so many stampings that can corrode from the inside out like the rocker panels, I use an expanding foam from the hardware store.
I open an escape hole for the expanding product at the far end of the cavity and shoot the juice in from the other end.
When it expands as it cures and drips out the other end overnight, I make sure I arrive late enough the next day so that somebody else cleans it up and tells me what happened.
I always look shocked and thank them for the advice.

[Sumner]

First paint what you can with PPG's DP-90 or a different number depending on the color you want.  This is a great epoxy primer.  Then top that with a high build primer if you want and a color top coat if you want.

Next at the auto paint store get a seam sealer like 3M's. It will stick to the paint (I would use it with one of the primer steps) and can be painted and will stay in place and is somewhat flexible.  It is good stuff.  You use it on older cars for like the drip rails and body joints. 

Where I've painted my frame and body with DP-90 first on my pickup I've never had any rust.  My problem was I made the bed from scratch and where the bed supports are by the sides I have the problem you are talking about since there is no paint back in there.  When I redo it I'll use seam sealer in all those places.

If you can paint the pieces throughly with the DP-90 before assemble you should be good to go even without the seam sealer, but if there is cracks that haven't been painted on all the surfaces in the cracks use the seam sealer.

I have a section on my site with my body work suggestions:

http://purplesagetradingpost.com/sumner/techinfo/tech--body-paint-index.html

Also if some of you have only been going to my Bonneville pages you might want to check my tech pages here:

http://purplesagetradingpost.com/sumner/techinfo/techinfo.html

c ya,

Sum

[Milwaukee Midget]

Curious as to the extent of the rust.  You talking holes, or just surface?

[John Burk]

When it goes back together how about zinc washers as standoffs where the body bolts to the frame as sacrificial anodes . Salt could be pressure washed out of the gap and the remainder around the washers would ignore the steel and work on the zinc .

[JackD]

Using a sacrificial washer in a structural application is sacrificing the structural integrity of the assembly.
I use as many Stainless Steel fasteners as I can because they will outlast the racer and don't contribute to the corrosion problem.
When you drop one in a belly pan and gan't get it back , even with a magnet, just get a lot of help, turn the racer over, and shake it.
It works everytime. 

[Stan Back]

Thanx for all the replies so far.  I'm learning.

Th rust is all surface-type -- no holes in the 1/4-inch frame.  The main problem is in a flange that runs laterally to the side of the top of the frame.  It conforms more to the shape of the underside of the body and rust gets in the seam formed by the frame channel break and the 90-degree back side of the flange.

I'm planning on putting rust-stop in there, maybe bondo-ing in the void and repainting with the industrial "tractor" paint that has worked good for me.

I like stainless fasteners -- I just need to more consistantly put anti-seize on them!

Still would like to find a foam product to fill the void and keep the water out.

[Dean Los Angeles]

Still would like to find a foam product to fill the void and keep the water out.

Keeping water out works if it was designed to do that. After the fact, over inconsistent surfaces, is likely to leave some tiny void for water to get in. Once it's in, it will never, never, never dry out. And you will never see it. Grease works well for filling a small void, and if you put a zerk fitting on it you can pump new grease in and pump the old stuff out.

[836dstr]

Stan,

To make my floorboards removable I had used 1/8" steel panels that I prepainted and pop-riveted to the frame and crossmembers. I then coated all of the seams with "Body-Tec ultra flex brushable 4164" seam sealer that I ordered from "Eastwood". I applied it with a cheap acid brush using 2 coats. It's consistancy is something like axle grease and is pretty sticky. It's easy to work with and should seal a 1/4" gap with no problem.

Tom

P.S. HAPPY THANKSGIVING !

[Sumner]

........................I'm planning on putting rust-stop in there, maybe bondo-ing in the void and repainting with the industrial "tractor" paint that has worked good for me..................

Don't forget that bondo absorbs moisture.  If you go with something along that line use Marglass which is will not absorb moisture.  You mix it like bondo and apply it the same way, but it doesn't sand as good as bondo.  Anytime I mig holes shut or put in patch panels I use the marglass for the first layer.  It will fill pin holes in the welds that you don't see and stop moisture from coming through.  Grind it down and then bondo over that before the paint.

Do it right in the first place with a good epoxy paint and you won't need any of the rust products and if it was me I would save the tractor paint for your tractor .  The PPG paint that I mentioned can be found at most auto paint suppliers and will last forever and the seam sealer Tom is talking about is the way to go.

c ya,

Sum   

[Seldom Seen Slim]

Stan:

When you're shopping for stainless fasteners -- get REAL ones.  There's a long discussion of the various grades available somewhere in the archives.  Don't do like I did when getting stainless for the little stuff -- the tarp hold-downs, trailer bolts to hold the hooks on the floor, etc.  Those "stainless" fasteners usually have a little coating of rust on them by the end of the following winter.  I guess our local Ace hardware isn't "the" place.

Gotta have absolute corrosion proof fasteners?  Brass -- but don't expect strength as well as no corrosion.

[JackD]

Green on the surface of the brass is brass too and just an "optical conclusion" ?
The anti-seize that many use on stainless fasteners is mostly related to  the thread cutting tooling that produces a tighter fit as the tool wears.
Some of it comes from surface contaminants that build up on the part from the environment and the grease coating just provides a barrier.
Growing old around boats and boat people will learn ya a lot about the chemistry and economy of that kinda stuff.
In 1928, my grandfather visited the ship my dad was assigned to and during the tour was seen to get out his trusty pocket knife and cut away some paint to see for himself if it was steel or wood under there, because everybody in his circle knew an all steel boat could never float.

"I guess ya kinda learn as ya go, and the important part of that is ya gotta keep movin." (Bob Higbee-RIP)

[Dr Goggles]

Still would like to find a foam product to fill the void and keep the water out.

Keeping water out works if it was designed to do that. After the fact, over inconsistent surfaces, is likely to leave some tiny void for water to get in. Once it's in, it will never, never, never dry out. And you will never see it. Grease works well for filling a small void, and if you put a zerk fitting on it you can pump new grease in and pump the old stuff out.

I'm doing a little( I jest , it's gobbling up time frantically) preventative maintenance on my '64 panelvan......The last time I drove it was to the salt in March '06.....I spent a day washing it down when I got back...then parked it for eighteen months on the dirt ....It hasn't had a full resto in the fifteen years I've had it and hasn't really had a proper underbody coat on it for a while either.......Now it's on a rotisserie and I've cleaned it up , blasted it where it was that familiar reddish color and am getting ready to paint it with , whaddayaknow??? PPG epoxy primer.....I'm doing this because I want to keep the car , but not use it for a while....any way the point of this story( yes there is one) is to tell you about the factory installed system that kept most of the floor pristine for 43 years.........It's been leaking  like the bloody Exxon Valdez since the day it was built , yes it's as simple as tipping oil in the top of the motor and then various forces generated by it help to distribute the oil evenly all over the underbody where it acts as a moisture repellent. I'm now nervous about the fact that having washed it out of every nook and crevice that I have to get the PPG to get full coverage or I've actually made the situation worse....this could be a lesson not to mess with natural systems.

Interestingly the soil in the area of lake Gairdner is bright red ..they mine iron ore in the area....everything looked worse under the car because it was coated in a layer of this red iron oxide .......so I was relieved that a lot of it was pigment rather than trauma.....

A simple understanding of the chemistry of oxidation will help you understand what will lesson your rust problems , keeping water away from bare metal is one of the keys , metal mixing is the other.

[Richard Thomason]

One other little thing to remember about rust and corrosion on the salt flats, anything that's out there is subject to the corrosion factor. It can be locked in a tool box and never opened or taken out of the trailer, but it still can and will rust. We've learned that lesson very well thank you.