AMS-M-3171 Type III
DOW 7 is typically used for both new and overhauled parts that has dissimilar materials where conditions will tolerate a less robust alternative than anodize coatings. This film is extremely thin and has very little corrosion resistance. The primary purpose of this coating is to form a thin film which will promote paint adhesion. Much like DOW 19, the DOW 7 is also a chromate chemical conversion coating. Chemical conversion coatings, when applied to magnesium, have chemical reaction which results in a thin film being formed on the magnesium surface. DOW 7 also contains the toxic chemical hexavalent chromium (aka:Cr6+). The primary drawbacks to these coatings are that they have little to no corrosion resistance.