Coating underneath Keystone 5th wheeler

[suescottnz]

We recently failed the Warrant of Fitness test (NZ) because of some rust underneath the van. We took it to a tradesman to have it sandblasted but he was not willing to do it because he didn't know what was underneath the coating which could be damaged.

Can anyone tell us what the coating is? Is it safe to sandblast the underneath without damaging anything? If not what are our options?

Hoping someone can help us.

Cheers

Sue and Roger

[JRTJH]

If you're asking about the "Corrugated plastic sheeting" under the trailer, it is called "Coroplast" and is nothing more than a plastic barrier to help protect the belly from getting wet when towing. Under that (actually above that) is the metal frame, wiring plumbing, mechanisms for any electric/hydraulic slides, some propane runs from the main black iron gas pipe that travel through the belly and up into the coach for each gas appliance (stove/oven, refrigeraor, water heater, furnace).....

I would not expect that the coroplast would survive an aggressive sandblasting.

The actual frame for the trailer, if it is a Lippert I beam frame, is cheaply painted with whatever meets the air quality standards at the time of manufacture. That changes frequently, depending on what type of air filtering system they have on their paint booth. If your trailer has a NORCO "Huck Bolt Frame" then it is powder coated....

Your trailer was shipped to Australia where it was "converted" to your standards (12 wire umbilical I believe) converted to 240VAC with appliance changes, and several other "conversion requirements to meet your import standards.... There may be a "mandatory coating" that is applied after it arrives from the US. If that's the coating in question, then it's not OEM, but I'd suspect you would be familiar with that coating if it is a "local to your country coating requirement"....

I "think" you may be talking about the black plastic "sags in the middle" coroplast..... That'd be my "best guess"... and no, it won't hold up to sand blasting.

[suescottnz]

Thank you so much for your detailed message, John, although the message wasn't what we wanted to hear. We're actually in New Zealand but the forum didn't have a place for us so I put Tasmania as the nearest place. All that is irrelevant. The problem we now have is a 5th wheeler that can't get a warrant and we can't remove it by sandblasting. We shall have to work out if the job can be done by hand but that is likely to be very expensive. At this stage we don't have a lot of choices. I need an emoji which shows me crying. Thanks again. It removes uncertainty. Sue

[JRTJH]

Sue,

The coroplast cover is removeable. There are a large number of self tapping screws and/or pneumatically installed "nails" that go into the bottom of the
I-beam frame rails to secure it in place. Your repairman can remove some of those and drop a section of the coroplast or remove them all, CAREFULLY remove the coroplast, sandblast the rust, treat it with whatever is recommended to pass your inspection, then reinstall the coroplast using self tapping screws that are slightly larger than what was removed.

Also, I'd recommend using "fender washers" on each of those self tapping screws. If you/the repairman is not familiar with that term, fender washers are simply large 1.5-2cm washers stamped from light duty metal. Their purpose is to prevent the head of the self tapping screw from cutting through the coroplast upon reinstallation.....

Hopefully the repairman can get access to the rusted components by just removing a part of the coroplast, holding it down with a heavy weight, doing the rust removal and then reinstalling it.

Keep us posted as you talk to him about that possibility. I'm just one of a number of members who might have ideas about how to complete this task, so if that doesn't work, don't give up, just let us know and hopefully someone else will post a different approach that might help you get back on the road and traveling with your trailer again.... GOOD LUCK !!!!!

[suescottnz]

Again thank you so much for taking the time to explain this to us.
Extremely grateful.
Sue

[wiredgeorge]

Wish the OP would post some pictures of the rust area. If the frame or fittings are rusting, the metal is ferrous. A diluted phosphoric acid solution will neutralize the rust and turn it inert and it can be painted. This is what is done with steel bridges in the USA where it isn't possible to sand or sandblast the rust. Any loose rust has to be scraped and the phosphoric acid solution can be brushed or sprayed on the rust surface. I used this technique for many years for motorcycle gas tanks which are plain steel and rust on the inside and need treating. Severely rusted and they then need coated with a epoxy made specially for the purpose else the tank will develop pin holes and these will quickly ruin a nice paint job.

[suescottnz]

Thank you for you comments also. I will put some photos up. Roger got underneath today and took them. His mind is willing to do the job but the body is weak. The coroplast appears to be stapled up rather than screwed.

[suescottnz]

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[TXiceman]

How old is the trailer? I think you are left to hand clean and paint. Either avid wash or wire brush and paint with a good rust proof primer first.

Lippert does not even clean the surface rust.... just pant over the rust. Sadly, Lippert supplies 95% of the RV trailer frames in the US.

We had HitchHiker Champagne with a powder coated frame and no rust after 10 years on the road.

This trailer is my first and last Keystone product.

Ken

[suescottnz]

Dear Bryan
The van is 10 years old. We are taking it into a local guy on Monday to see what he can do.
Thanks for your input.
Sue

[Alibaddy]

Loctite makes a product called "Extend" in North America in gallon pails and spray cans. If it is available in your location, it is excellent to convert rust and treated steel surfaces will never rust again. The loose rust should be scraped away, but the product must be applied to rusty steel. It will turn black, and doesn't need to be painted, unless you wish to do so. I have used this product to salvage the frames of equipment in a wet environment of a dairy plant, and on outdoor equipment. In the latter case, the equipment was still showing zero signs of corrosion 26 years later.

[wiredgeorge]

Originally Posted by Alibaddy

Loctite makes a product called "Extend" in North America in gallon pails and spray cans. If it is available in your location, it is excellent to convert rust and treated steel surfaces will never rust again. The loose rust should be scraped away, but the product must be applied to rusty steel. It will turn black, and doesn't need to be painted, unless you wish to do so. I have used this product to salvage the frames of equipment in a wet environment of a dairy plant, and on outdoor equipment. In the latter case, the equipment was still showing zero signs of corrosion 26 years later.

The Loctite stuff is formic acid and acetone. It does exactly what phosphoric acid does and a phosphoric acid solution isn't nearly as expensive. Try it next time you want to kill rust. It is what they use on bridges that are over salt water prior to paint.

[Alibaddy]

Will the phosphoric acid leave a black finish that doesn't need to be painted? I don't know if I can buy phosphoric acid in Canada, but the information is interesting.

[wiredgeorge]

It turns the rust black but I would then paint the area. It is fine to paint right over the inert substance the the phosphoric acid leaves. I can buy it at any home improvement or hardware store.

[jasin1]

This is what a lot of people talk about and use on the Jeep forums to take care of the poorly designed jeep tj frames that didn’t come with a drain hole in a critical spot…. another good but expensive solution is Eastwood…they have a bunch of products and videos for dealing with rust.. .Although Georges idea seems much more cost effective… https://www.eastwood.com/rust-solutions/treatment.html

[Sulphur1]

Hi Sue & Roger. I'm across the ditch.Look up Phoenix Metalfix NZ. Unless the rust is extreme you just need too go over it to remove any surface 'scale' and apply the Metalfix. It is water based, and has phosphoric acid.to neutralize rust and seal it off. Excellent product used by farmers in the know. PM me if you want more info, I have the coreflute off atm. Cheers Jon

[Stircrazy]

Originally Posted by jasin1

This is what a lot of people talk about and use on the Jeep forums to take care of the poorly designed jeep tj frames that didn’t come with a drain hole in a critical spot…. another good but expensive solution is Eastwood…they have a bunch of products and videos for dealing with rust.. .Although Georges idea seems much more cost effective… https://www.eastwood.com/rust-solutions/treatment.html

we used to use similar products to treat areas on the navy ships, you can get cheaper forms of it.. they basically convert the rust to a magnetite and have a latex primer built in so you can paint right over it when it dries. that stuff works great.

[suescottnz]

Thanks for your input
Sue