Why the end of the aluminum coil will have a yellow spot?The reason may be that the manufacturer is not cleaned, and must be carefully cleaned before coating, or there may be paint fall off phenomenon.Without coolant processing one, to see if there is no stain, so you can engage in removal of cooling liquid is not interference. Blank surface should have a layer of alumina film processing, heat, such conditions should make the cooling liquid and the alkaline layer friction reactionThe reason may be that the manufacturer is not cleaned, and must be carefully cleaned before coating, or there may be paint fall off phenomenon.Other related question