Stripping and painting chassis before welding

[Shakey]

Hey folks, I'm new to this restoration and have a bit of a question/best practice regarding the chassis.

Before it goes off to my fabricator/Landy nut mate for welding I'm going to strip the chassis to check for any unseen problems.

My question is, should I paint the spots that are OK with the first coat as I go (to avoid surface rust) or wait for it to come back and give it a quick once over before painting it in one go?

Its likely to be a few weeks between striping and getting it back, also repairs will be at the least to rear cross member, dumb irons and one out rigger.

[Lotz-A-Landies]

Having had both sand blasted chassis and caustic stripping of chassis, although expensive I've become an fan of the caustic stripping method as it gets to rust both inside and out as well as removing the paint.

Its a good idea to do one or the other before taking it off to the welder as it will identify areas that need repair.

If you do either make sure you do a phosphate wash or coating inside and out as soon as possible to inhibit rusting.

[Shakey]

So once the chassis has been stripped, should I paint with penetroil and then coat with primer or just prime and use penetroil as a thinner when painting?

[DoubleChevron]

I thought most used the moisture cured urethanes these days on chassis (eg: kbs/por) You can just brush paint it that way :)

seeya,
Shane L.

[workingonit]

I would not recommend covering your chassis with urethane, if thats the intention, and then sending to your welding mate. Heated urethane still has the potential to release cyanates according to the spec sheet I read.

I would recommend you chemically strip, then weld, sand blast and paint. Phosphating the inside of the chassis sounds like a good idea, interesting to hear how people have done it.

I'm using paint stripper, then garnet blasting, followed immediately by kbs urethane brushed on. The blasting provides a clean and keyed surface.

If you are only chemically or mechanically cleaning, and find you have small amount of oil staining and rust dimples then use manufacturers 3 stage process. Degrease and wash. Then phosphate and wash - you'll get a change in colour when dry but don't try and remove. Then urethane paint.

If sandblasted then no need for degreasing or phosphate, just the top coat - assuming you avoided handling the blasted area, and your blasting took out rust in the dimples.

Paint stripper hurts on bare skin so water handy and it eats nitrile gloves

Unless you have a filtered spray booth, you are completely covered head to toe and full face independent air supply do not spray paint with the urethane as it contains cyanate.

Someone recommended water base industrial coatings by Pheonix in Perth. Anyone been able to compare them to urethane?

Don't use chlorine based oil cleaners and the like as the arc turns the chlorine into phosgene. http://www.brewracingframes.com/safety-alert-brake-cleaner--phosgene-gas.html

[DoubleChevron]

the cheapest way to strip a chassis is to probably buy a box of those "strip it" discs for your 4" angle grinder ... and get too work. It'll be slow, horrible, messy, wont' get into the difficult to access places. But it will also be easy and effective.

You could do sections of the chassis at a time and brush coat soon after clean/stripped.

this sort of thing

4 X 125mm 5" Poly Strip Disc Wheel CAR Paint Rust Removal Clean Angle Grinder | eBay (http://www.ebay.com.au/itm/4-x-125mm-5-POLY-STRIP-DISC-WHEEL-CAR-PAINT-RUST-REMOVAL-CLEAN-ANGLE-GRINDER-/170793937178)

seeya,
Shane L.

[isuzurover]

If you are going to the trouble i would get the chassis galvanised after welding.

[Shakey]

For clarification, my intent is to strip the chassis (with those discs) then do a first coat to stop surface rust between striping and welding. Then finish painting after welding.

[DoubleChevron]

I'd think the easiest way to proceed would be to do whatever repairs are required... Then strip the chassic and coat it. Otherwise you'll be re-doing the repaired areas all over again after the repairs are done.

seeya,
Shane L.

[isuzurover]

For clarification, my intent is to strip the chassis (with those discs) then do a first coat to stop surface rust between striping and welding. Then finish painting after welding.

In that case don't bother. Just go over the chassis with a slag hammer and look for anywhere that needs repair. Just sand those sections back. Do the rest after you get it back from the welder.

I would still advise galvanising the chassis if you are going to that much trouble though.

[workingonit]

Double>> i've used those strip discs as well - they are far superior to wire wheels in my view.

Problem with my chassis is that a previous owner attempted to apply some sort of solid wax in most places, at least 1-2mm thick. If the strip disc picks up this wax, or grease for that matter, it continues cutting but adding a smear as it goes, requiring more cleaning. That's why I resorted to chemical stripping as it deals with the wax and grease.

I agree it is a wast to do the quality strip before welding. I found the chemical strip was good enough to get rid of the bulk crud to expose issues. Then exposed, you get a little surface rust. Then weld. After welding do the quality strip ie sandblast, then paint top coat straight on, as generally no need for degrease or phosphating.

Zinc bath in Darwin was going to be about $700 at a trailer place. But since I don't have a trailer big enough and zinc man concerned about warping I dropped the idea and decided to paint.

But I would go your way if Shakey is not blasting.

[DoubleChevron]

Do you have a pressure washer :confused:

Let the chassis sit in the hot sun to soften the wax and spray export degreaser all over this ... then hit it with a high pressure washer (use hot water if you can). That may remove all of the wax that's causing issues.

https://www.aulro.com/afvb/images/imported/2015/01/497.jpg

this is the crap that was all over the engine bay of one of the cars I'm tinkering with at the moment. It was huge fun to strip too. I reckon it's 50year old brake fluid mixed with oil and dirt.

seeya,
Shane L.

[workingonit]

Pressure washer is on the 'to buy' list, something descent though - spare coin is going on the RRC conversion at the moment. And having one will just create more work...the house exterior...the tractor...the pathways...the kids bedrooms...