Rust

[Paul Dawson]

Sorry to use a swear word as the thread title - but whilst I know my way round a set of spanners bodywork is new to me.

Just wondering......I spent a lot of time with a wire cup and a powerfile under my Viva getting as much surface rust off as I could. Then I coated the whole lot with two coats of Dinitrol Converust.

Some bits needed welding so I left them bare, other bits I gave a coating of Dinitrol Underbody Wax 4941 just to keep them protected whilst it was at the welders.

The car has been away about a year kept indoors in a workshop whilst the guy did the welding in his spare time. It's now back and MOT'd so I'm going back to the areas I worked on over a year ago. Here's the thing that puzzles me....

The bits I left bare are solid, no sign of any rust at all. But the bits which had Underbody Wax sprayed over them are showing signs of slight surface rust. I'd have expected it to be the other way round.

Any ideas why this has happened? All areas were treated the same - the only difference is wax or no wax. Yet it is the waxed areas that have signs of rust.

[rizzo]

Confused a bit, you say the bits that needed welding you left bare, so surely those areas have fresh steel on them if they have been welded hence no rust, ?

[Paul Dawson]

I left the general area around where welding needing doing bare. Eg - it had new inner wings fitted so I stripped the wheelarch area and left it just with a coating of rust treatment on it - and the metal has no sign of any rust on it at all. Whereas the underside of the floorpan which was treated exactly the same, and then had wax over it, has slight signs of rust appearing.

It's nothing major, I'm just baffled why metal with wax over it has rusted whereas metal left with just the rust treatment hasn't.

[shamm]

If water can creep under the edges of the under seal then it holds the moisture against the metal causing rust!