I have a Bucket full of UNDERCOATING! Miserable job chipping it off. Major PITA! You cant see the metal under 1/4" of rock hard undercoating chip chip chip, tap tap tap, scrape scrape scrape till your arms fall off, Oh and don't forget that every ten taps you miss the chisel and strike your VERY sore knuckle. So how does it go "chip chip chip, tap tap tap, scrape scrape scrape thud #*&$#$!!!chip chip chip, tap tap tap, scrape scrape scrape thud #*&$#$!!! Rinse and Repeat
You cant see the metal under 1/4" of rock hard undercoating 
chip chip chip, tap tap tap, scrape scrape scrape till your arms fall off, Oh and don't forget that every ten taps you miss the chisel and strike your VERY sore knuckle. 
