I picked up an OE trunk lid last weekend. Mine is rusted out. but there is some surface rust in between the lid skin and the underside of the trunk lid. How do I get in there to seal the surface rust, sand and por15 it. Do I have to seperate the trunk lid somehow?

I would suggest treating it similar to a gas tank. Use a mild acid to eat at the rust. Turn the lid upside down and pour in some muratic acid and let it slosh around inside there. Wait about 10 min and flush it with plenty of water, then have a look in the holes. If it needs another treatment, do it again, and check. When it looks pretty clean, then use an alkali solution to pour in and neutralize the acid. Baking soda and hot water will do the trick. Flush it well with water then drain it and use a fan and air compressor to eliminate all the water inside.
Now you can coat it inside with a sealer, such as a gas tank sealer or thinned down POR-15 or what have you.
The problem is that GM never went to much care in preventing the rust to begin with. Now we have to be inventive to preserve the parts.

Dan

I ruined a really nice one by sandblasting it, so don't try that.

Rob

Muratic acid, is that like swimming pool acid?

Great, that sounds like a good plan. I appreciate it.