Rust proofing on inaccessable car repairs?

[Alec]

OK. So I bought a Clarke 135TE a few months ago. I've been gradually learning to weld. I just had a quick question on how to add some rust resiatance patch repairs.

Say, for example, I'm patching a box section. Once I've completed the repair I'll apply the same brushed paint reatment to the face of the reapir as the rest of the chassis i.e. POR-15. But how to protect te inside face of the reapir within the box section?

I've been spraying Dynax S-50 cavity wax through the drainage holes in cavities that don't need repairing. The can comes with a 90cm flexible lance so that you get good coverage. Would this be sufficient to protect the metal from long term corrosion?

Other treatments I'd thought of:

1. Weld through primer - I'd need to use a metal fume mask I guess as welding inside.

2. Paint the inside of the repair with POR-15 paint - I guess it would catch fire or be compromised when I weld it?

3. Paint the inside with POR -15 high temperature paint (Black Velvet). I've been using it on my exhaust heat shields and can work up to 1200F. But I guess this too would fail/burn off at MIG welding temperatures?

Thanks for any ideas.

 

[keith19]

I guess it depends on how long you intend to keep the vehicle. I tend to keep mine going until they become classics...or unrepairables...

Personally I've always sprayed inside the welded panels with cavity wax like you're using, or waxoyl or something similar. When cash was tight I've just used strained engine oil and a pressure spray, but don't let the car stand on the drive afterwards.

Painting inside panels helps keep them from rusting too quickly, but as you say burns off near the welds. This is where the rust begins, especially if moisture can gain entry, so you do need the wax spray, even if you paint inside.

For long-term corrosion resistance we should really respray the insides of all panels about every 4-5 years, if not more regularly. But it's hard to remember to do this, so they start rusting out in a few places after maybe 8-10 years and have to be repaired again.

The Mods should maybe move your enquiry to a new thread?

 

[Alec]

I didn't want to clutter up the place with lots of new threads with individual questions - but I guess it would get more attention that way:-)

 

[rtbcomp]

Oil from an engine is a no-no because it is carcenogenic and acidic if water gets into it.

Oil from an axle or gearbox may be OK, I've heard of people thinning it down with paraffin.

A friend of mine used to dissolve blocks of lanolin in paraffin and spray it on.

You have to keep oil away from rubber bushes & pipes, whereas Waxoyl is ok.