that pickling was from the steel maker, not GM, it's a common process in steel making to descale new metal and results in rapid surface rust if not oiled ... has nothing to do with how well the frame stood up for 60 years
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics