hi kit g, roland and dan pag- back in the war these anti rust potions were widely sold and then pretty much disappeared. problem is two fold spraying this magic juice in door boxes, rockerpanels and other hidden rust prone spaces is very hit and miss because you cant see what you are coating. after drilling a hole you would spray and then use a plastic plug to plug the hole. problem is spots you miss inside will rust laterally . the other problem is the guarantee. I read a few of them and they all had as the sole remedy if rust occurred a refund of the purchase price or a respray, no rust damage repair. sages of yesteryear said the only effective way to spray these juices was to do it on the sheet metal before the car was assembled in the factory so no spot would be missed, but that generally wasn't done. this could cause car enthusiasts to make accusations of shysterism and have a generally bad attitude to these vendors. rememba what inspector Renaud said to wit -im shocked, shocked that gambling is going on here(substitute shysterism). recommend all read each word in their vendor invoices, contracts and warranties. thanks tons oldduke