Rust proofing inside box sections

[pmdavies]

Hi everyone

So the Morris is on its side and the amateur welder's been let loose on it (that's me!).

What's worrying me is I'm spending lot's of time welding and sanding and painting the underside but how to I protect the inside of the box sections.

Do I spray Waxoil or engine oil in them or something?

+ what do I do with the existing box sections that already have some internal corrossion (some with patches ect). Is there any point in spraying Waxoil into an already partially corroded section?

Many thanks for sharing any experiences on the subject.

Pete

[Dean]

I've used a rust converter, poured it into a parafin gun, attached it to my compressor and blasted it down.
- The chassis legs
- Sills
- Rear arches from the inside of car.
- under the rear seat
- centre door pillars via removed bolt in door hinge.
- front door pillars through bolt hole.

A parafin gun really vapourises the stuff and blasts it long distances without thinning. The rust stuff I got it from FROST for about £15 a litre.



I'll leave this a week to go hard then do the same again but with waxoyl.

RUST STUFF
http://www.frost.co.uk/item_Detail.asp? ... ubCatID=34

PARAFIN GUN
http://www.machinemart.co.uk/shop/produ ... -spray-gun

[Stig]

I'd recommend spraying repair sections with weld-through zinc primer before fitting as you'll never get at everywhere to paint afterwards. Then spray with waxoyl etc. - waxoyl, steel box-section and a MIG welder makes a good flame-thrower though so finish the welding first!

[bmcecosse]

Sprayed-in rust killer is about all you can do. Followed by Waxoyl.

[neiltomlinson]

hi i would do the same as dean said when you do the waxoyl i use black do not thin to spray
put the parafin gun can in hot boiling water for a little time this make the waxoyl thin & easy to spray use stright away & the other thing i do when you are doing under the car dont use waxoyl neat because allway stays sticky if you mix 75% waxoyl & 25% underseal this goes on well & last well do all my car like this neil

[aupickup]

use clear for inside box sections
also outside

at least then you can see if any issues arise rust wise and act on it quickly

[Chris Morley]

+ what do I do with the existing box sections that already have some internal corrossion (some with patches ect). Is there any point in spraying Waxoil into an already partially corroded section?

I would say yes - but only once you've cleared away any the rust scales, dirt and peeling paint and have dried any remaining moisture. I recall using a vacuum cleaner with a crude taped on extension to clear all the crud from a chassis leg before spraying inside it.

I doubt that spraying waxoil onto damp and bubbled up rust will slow it down much. And of course if that section needs further welding in the near future you have a good chance of setting it alight!

[Mick_Anik]

A guy who restores tractors advised me to use used diesel oil in treating vehicle box sections. He told me this was the most effective treatment he had ever found.

I tend to agree. I have done this often, and years later have had no problem with developing rust. He said it was better on metal with a bit of surface rust, rather than new and untarnished. Like with Hammerite...it seems to stick on better to brown metal rather than new and shiny.
I re-treat as often as I can be inclined to. Stand the car on old carpet and sheets of carboard to protect the environment, and pour loads in, jacking the car up back and front alternately so it flows everywhere. Then make a brush on a long wire to get the oil up higher inside the enclosed areas. The car then has to stand for a few days for the drops to stop falling.....one day level, one day with the front up, and one day with the back up. Another day level just to make sure.

This I do after everything on the outide has been painted, once the welding is finished, otherwise it's a lot of cleaning oil off before the paint goes on.

This is one of those subjects....ten people, ten opinions! My view is that after a year, the oil picks up sand and dirt, so with subsequent treatments, a substance similar to that which you find on the chassis around leaky engines builds up......and there's never much rust, if any, under that stuff! So after a few treatments, you have a nice, thick, gungy, water-repellent layer inside the sections.

As I understand it, there is no way you can do a 'once and forever' treatment.....anything you do has to be maintained, like everything else.

[pmdavies]

Thanks guys, some interesting ideas.

How much of a problem would I be creating for future welding if I spray Waxoyl or engine oil in the sections?

[Mick_Anik]

Well, anything oily or waxy will start dripping down once it gets hot. Welding from above would be better, as nothing drips upwards, but you'd have the evil smoke to contend with.

In the past I have had to weld to burn stuff off until it stops dripping into the weld area, grind that weld off, and then do the 'proper' weld.

So in answer to your question.....yes, it can be a bit of a pain. I pay particular attention to the lower areas. I seam weld the inside joins of the welded elements as much as I can - nothing drips through a seam weld.

So, say on a full sill job , you can do the top of the box section last, allowing you to weld the interior joins beforehand. If I were only replacing the bottom element of the sill, I would later cut the top off, even if were okay, so I could weld up the inside joins. Then I'd weld a new top on from new steel. I only do my own cars, so I can afford the time. Also, I made be slightly mad !

Worth the time to do this, though - everything is in place and clean after the exterior welding. And if an elements corrodes and ever needs welding again, you would have a nice line of weld to weld it too.......I've never seen weld material rust away.

Only weld half an inch at a time, so the steel doesn't get too hot and result in distortion. I do a short weld, then move on to the next as far away as possible, and keep going until everything is joined up. Obviously, as the gaps to be welded get closer and closer together, some waiting time comes into it. Just enjoy the music you should have playing during these 'down' times.

The secret of getting a good result is patience - oodles of it!

Just think ahead, and everything should work out fine.

[Chris Morley]

Only weld half an inch at a time, so the steel doesn't get too hot and result in distortion.

Good advice - also it only sets fire to small amounts of waxoil, so you have a fighting chance of blowing it out!

[Mick_Anik]

Yes, another very good reason to weld slowly. I weld with a hosepipe and a fire extinguisher to hand.

Another thing...I cannot do welding 'on the clock'. It takes as long as it takes - good days, bad days, good pieces, bad pieces. It takes about an hour to set up and get into your stride with it.....then there's a 'peak' of performance, which depends on your stamina. As soon as you start to think "I've had enough", it's time to pack up welding for the day! You can draw the proceedings to a close by doing something easier, like painting what you've completed.

Grind down the welds as you go, to save doing a lot at once later. Nothing quite as grim as grinding non-stop for a long spell.

Be careful, and enjoy the process....it's very satisfying.

Please excuse the digression away from the question, but safety and comfort advice cannot be repeated too often, IMHO.