How do you deal with light rust at the bottom of the door on the inside and inside the trunk lid, between the two layers?

 

Most people just ignore it, since they garage their cars and that rust will never get any worse.

You could spray it with oil if you want, or try to de-rust and paint it, but that would require complete disassembly of the doors to be really effective.

- Eric

 

If the parts are still on the car, use some clay or putty, and block up the drain holes. Then pour in some metal prep. like Dupont 5717S, or Picklex. Let it sit for a while (10-15 min.) then remove the putty, & drain it out. Most preps will leave an iron phosphate film , that is a bit resistant to rusting, but for better insurance, coat it with a rust preventative, like Master Series, or POR-15. Check to see if you have to neutralize, or flush the metal prep first, though. Should be in the instructions for the preventative.

 

I'll just add to the previous post that often the rust is caused by debris that settles into that joint and retains moisture. If possible, you should try to remove any dirt, leaves, etc that are in there first, and be sure to clear the drain holes before starting. Once you've done that, the Picklex process described above is a good one.