got the usual aluminium rust in the normal place (lower connection to bulkhead).

I'm in the middle of replacing my bulkhead, so will be tarting things up as they go back on. Trying to decide if I need to replace this lower wing, or if taking it back to metal and re-spraying will do?

One paint shop I spoke (before I decided to do it myself) said that if painted, the bubbling will be back in 18 months, so I'm best replacing the panel. I don't understand why that would be!

That looks as though someone has been grinding ferrous metal nearby and it's gone rusty underneath the aluminium.
I suggest that you polish it out using a 500-grit flap wheel, and then, once you've flattened it, immediately paint on an epoxy to seal against contact with our (generally) moist air!
You can then touch it up using your Landy primers and topcoat.

I had my Defender resprayed 12 months ago by a professional garage. They sanded the bubbling down to bare metal before respraying it. The bubbling started after 7 months. I would replace the panel if you want to the job done properly..

yu will need to do the inside as well. Ensure you used acid etch primer too.

Stick some thin checker plate over it, same otherside.
Just a suggestion

I'll be reprinting the whole thing. I need to buy so many 'bits' while doing it, so replacement is only if I must!

Interesting about your paint job, mikescuba!

I can't see how the rot can return if I remove the paint and re-spray on both sides!

Checker plate is my last resort- hoping to get a good finish with paint for now...

Rorie said:

I'll be reprinting the whole thing. I need to buy so many 'bits' while doing it, so replacement is only if I must!

Interesting about your paint job, mikescuba!

I can't see how the rot can return if I remove the paint and re-spray on both sides!

Checker plate is my last resort- hoping to get a good finish with paint for now...

Click to expand...

The steel wing brace bar behind the wing might have started it. Or, a break in the paint somehow.
When the aluminium oxidises the oxide takes up more space than the aluminium on it's own did. It will expand under the paint and probably cause microscopic cracks in the surface of the paint. This will allow more air and water in and the process will soon speed up. You've got to get it back to shiny aluminium, use an etch primer so that it keys in to the metal better. You're hoping not to trap microscopic amounts of air up against the surface of the aluminium. If you think about the holes on a microscopic level, you can imagine this is tricky to achieve even on a new bare panel. On a panel that is damaged and pitted by corrosion, it's a canny bit trickier! We've all tried it though! Everyone will tell you, with paint work it's all in the preparation.

If you do decide to replace I'd recommend trying to get a genuine wing that's in good nick. Had a after market replacement on mine and it's a shocking fit. Didn't realize though untill after it was painted