What causes bad paint?

Looking at photos of some locomotives with paint problems I am not sure if the paint is. A: Falling off in chunks that can be picked up of the walkway (or chalking.) B: Not properly adhering to the underlying paint. C: Burning off (from Sun.) D: Fading untill the underlying paint is exposed. E: Rust getting under the paint causing it to bubble and fall off. F: getting so dirty the paint falls off.
For some locomotives like the Conrail C40-8Ws there was a bad paint batch and (certain) petroleum products can wreck havoc on paint. (Think fuel tank.)
http://www.trainweb.org/chessiephotos/p ... cs-c&o.jpg
http://www.trainweb.org/chessiephotos/p ... cs-c&o.jpg
http://www.railpictures.net/viewphoto.php?id=117989
http://www.railpictures.net/viewphoto.php?id=104756
http://www.railpictures.net/viewphoto.php?id=128961 (Rust under lettering on nose.)
http://www.railpictures.net/viewphoto.php?id=110417
http://www.rrpicturearchives.net/showPi ... ?id=201709

Most of those photos just look like paint that's past its prime. Paint's a consumable material...I don't think any manufacturer or railroad expects a paint job to last the life of a unit.

Some though do look like poor repaints -- like the Chessie unit with C&O blue showing through. But, the reality is, they just need a new paint job (unless they're about to be retired).

Hey octr202,

Can't help but notice your username...just wondering if you were formerly with the old Octoraro???

J.