Compressors must be drained after each use or rust can set up.

From the link below:

"This is an old sears belt drive V twin air compressor that was never drained properly. When air compressors run humidity in the air they compress condenses in the tank. The resulting water sits in the bottom of the tank until it is drained. When not drained regularly the tank will rust from the inside out, when the tank is weakened enough it will often fail catastrophically."

"Tanks have a maximum lifespan too. They still rot even with frequent draining. These compressors were built to replace in under 10 years. My personal shop compressor is built using a locomotive air supply tank ASME certified to 380PSI. The problem with that tank is, it's WAY too heavy for portability. So they make these thin steel tanks for portability thus the maximum life span. If a person really wants years out of a thin tank, they'll have the inside of the tank coated before the first use. Warranty void = yes. Life span increase = also yes. Pumps are another matter, few are built like they once were."

WATCH THE ENTIRE VIDEO - HE OPENS UP THE TANK SURGICALLY RUST RUST RUST RUST!!!! YIKES!!!!

https://www.youtube.com/watch?v=vdYimN5yOZc