As an engineer, I have to…
As an engineer, I have to reverse engineer a lot of parts, and need to know what alloy to specify. A strong magnet will tell me whether the part is 303, 304, 18-8, as it will be pretty strongly attracted. If it's very weakly, or not attracted at all, it's likely 316. Generally, the more magnetic, the less corrosion resistance, the easier to cut and form, and the less expensive the alloy is. These characteristics are consistent with what happened to the truck.