While working on my 67 we have been amazed how rust free it is. My question is however does rust start on the inside of panels and eat its way to the outside or not. Obviously if u have no paint or protection on the outside rust will start there but is this the source of serious corrosion or not? If it starts from the inside it means we need to go to greater efforts to seal the inside.
Comments?

It will find the best breeding ground and then choose the path of least resistance, wherever those might be.

Have you ever seen dew on your car before? You can have air inside your car that has a dewpoint that is lower than the ambient air temperature outside the car. At that point, the relative humidity inside the body of the car will reach 100%. When that happens, you get condensation internaly (less than full gas tanks as well). If the condensation finds an absorbant material(insulation or leaves for example), it will soak it up and be difficult to dry out. The moisture promotes rust.

You also get moisture inside the body from rain or car washing. That is actualy what was planned from the beginning. You have holes in the bottom of your doors for the rain/wash water to run out. If you have crud in there plugging up the holes, you have trapped moisture that is very difficult to dry out. These are just a few examples. There are draining/drying systems on other areas such as rockers and cowl plenums etc.

If you live in an area where they use salt on the roads in the winter, you can accelerate the rusting process.

-Mark.

Rust starts anywhere that gets wet and doesn't dry out well. On my car, that was on the lower front fenders just in front of the doors. Dirt and crud gets stuck between the rib inside the fender and the fender skin. Other places are rear window channel. Dirt gets trapped under the chrome strip and rusts through in the bottom of the window channel and up the sides. Window rust is worse if exsessive amounts of sealer (or silicon caulk) creates extra resevoirs of water / dirt. Lastly, my rear tail panel is rusting. At some point in it's life, someone removed the rear bumber and didn't seal the bolt holes when the bumper was reinstalled. The water wicked up between the panel welds and rusted through. Floor pans often rust if the windshield allows water to run down under the carpet and settle. There are others, but these are typical Camaro rust spots.

In general, an unprotected panel will usually only surface rust so long as it is able to dry out fairly quick. There are lots of areas inside the car that are unprotected such as the underdash area and under roof. However, those don't generally rust through since they manage to stay dry. In a humid climate the story may be different.

-dnult

Rust starts here in the great white north where you and I live!!! http://www.camaros.net/forum/biggrin.gif

Actually, up in the north country, the worst source of rust is all the little stone chips that leave the areas around the wheel housings, rockers, and floor pans open to the environment. If they salt/sand the roads when it snows in your neck of the woods and the car gets driven year round, that's all she wrote. You'll notice that all the old cars around your neighborhood rust in these spots first.

The other guys are right though, any unprotected surface that gets wet and never dries will breed cancer!

[This message has been edited by PDQUICK (edited 02-15-2003).]