That`s why I only use it for pinholes, once ground flush it`s not as strong as steel. surprisingly I welded through it not realizing it was there, it burned through rather well, unlike welding along realizing your running into lead. Whole nother matter. Lol. No matter how much you clean both sides of this old 40-60 year old auto sheetmetal your bound to get some pinholes, and the bronze works great. Lay 1/16 rod with tig right over the hole, with the current about 5-10 amps hotter and melt a small blob, hit the pedal full tilt and watch it sink in and no pinholes after you get off of it. you`ll grind more weld of the back side than the front. To each their own, use what works best for you.