Interesting. The Ford evaporator is probably an all aluminum coil and the irritant is the flux used to bond the aluminum to itself during manufacturing: Chemical: Aluminum Potassium Fluoride In Ford's case, the coil was not properly cleaned and defluxed during the manufacturing process. The coil itself is not degrading and producing the white powder.

The white powder you are seeing may not have the same chemistry and may or may not be hazardous. Is the coil under warranty? If so, the manufacturer needs to hear of this problem and may have an understanding of it already. Talk to them. You will need the coil model and serial number to expedite the discussion.