Yeah wash downs can be a problem. I work in a lot of super markets and even the use of 'Marine Grade' cord caps and outlets in wash down areas like the meat room, deli, prepared foods areas does not stop wash downs from causing problems.
For refrigerators the 2002 Handbook claims a common cause of refrigerators tripping the GFCIs is electric defrosting elements in the units.
This to me makes much more sense then the compressor tripping it. GFCIs can supply motor loads without a problem.
