I have had two cars complete soda blasted, soda blasting will NOT remove undercoating or rust. I removed the undercoating first, had the cars soda blasted, then any rust that was in structural areas we used STAR Blasting. The soda is great if done properly it will leave the phosphate coating on the original sheet metal, and the guy that did mine had NO warpage. The powder residue will get in to many areas not seen, so flushing will be needed but cleans up super easy.