axmonkey

I'm always checking out Cobalts on the road for rust trouble spots. Lately I've been seeing a lot with pinch weld rust below the rockers. I'd like to avoid this. I'm guessing step one is don't use the stock jack. Is it rock chip damage causing this, or is there some kind of water drainage at that point, or something else?

I'm thinking of just masking mine off and just undercoating the crap out of them.

steelmesh

I did/am doing an experiment with a Cruze. I put herculiner bed liner on the rocker panels and the pinch welds. In my Solstice I didn't herculiner it, but I did spray the internal cavity of the rocker panel with fluid film. Bed liners bond to paint really well, where rubberized underbody coatings have been proven to fail and in some circumstances cause accelerated rusting from water seeping behind the coating.

The rust will come from exposed metal caused by foreign object debris kicked up from the tires, rust oxidation is accelerated by your local climate. Smashing the pinch weld from a jack will damage the paint which exposes the metal to the elements. I machined a couple U shaped blocks to "straddle" the pinch weld, otherwise I jack from the suspension and suspension points.

Ask a Canadian, the proven effective method to prevent rust is to spray the underbody and body cavities with oils or waxes annually.

axmonkey

Bed liner sounds like a good plan! Great idea!