Ask the Expert Question-and-Answer Archive

by Ron Joseph

August, 2005

Color Changes (Color Shifts) in Paint Coatings

Q. I am using a aerospace paint (white) on some aluminium parts, some parts color changes to light yellow. I was told that it came into contact with Grease (LB7) over time. Is this normal? How can I prevent this from happening? It this due to insufficent cure time after paint?

A. There are several reasons why a paint might change from white to yellow over a period of time. Color changes can occur if you are not using a highly sunlight resistant resin; the pigments in the paint must be light resistant; contaminants on the aluminum surface can bleed through the paint and cause a color shift; improper curing of the paint can also be a cause of the problem; improper mixing or incorrect mixing ratio's can add to the problem.

I suggest that you consider all of these possibilities and try to eliminate those parameters that don't apply to your specific application.

Best wishes,

Ron Joseph