The Dow 7 magnesium treatment compound is provided as a pre-
mixed powder that is dissolved at time of use in 4 gallons of water.
This will produce enough solution for a 4-gallon immersion bath.
The complete process will require the initial activator solution which
is available as either Type I or Type II. Scroll down to the “Related
Products” section below to see the activators and description for their
proper selection which is alloy dependent.
Magnesium and its alloys are more galvanically active than even zinc
on the galvanic series. Magnesium will form a strong galvanic cell with
every other metal it comes into contact with and is always sacrificial.
When magnesium corrosion is detected, it requires immediate attention
or the corrosion will spread throughout the entire structure. Therefore,
these alloys must be properly protected from corrosion damage.
Dow 7 is a good choice for both new and overhauled parts that have
dissimilar materials such as inserts, or where conditions will tolerate a
less robust and less costly alternative to Dow 17 anodizing. It makes
an excellent paint base and provides the best corrosion protection of
the available chemical coatings for magnesium.
Dow 7 is a chemical conversion coating which results in no appreciable
dimensional change to the component. The surface of components coated
with Dow 7 is changed to a brassy or dark brown finish depending on the
alloy. Note that this coating film is dielectric (non-conductive).
The complete process requires two steps. The first step is an activator
immersion which is done at ambient temperature in the range between
70ºF and 90ºF. This is followed by a distilled water rinse.
The second step will require a stainless steel vessel that will allow
the heating of the Dow 7 solution to boiling point (200ºF). Immersion
time for the parts is about 30 minutes, also followed by a water
rinse before allowing to hang dry for 24 hours.
Specification & Certifications:
The coating produced by proper application of the contents of this solution
conforms to SAE AMS-M-3171, Type III (formerly MIL-M-3171, Type III),
sometimes referred to as “Dow 7”.
Not for use on the following magnesium alloys: EK30A, EK41A, HM31A,
HM21A, HK31A, La141A and M1A. Due to their chemistry, no coatings
form on these particular alloys.
Castings containing bearings, studs, and inserts of brass, bronze, steel and
cadmium-plated steel may be treated using this process. Note that aluminum
inserts will be rapidly attacked by the Hydrofluoric acid present in the Type II
Use alkaline cleaners containing less than 2% caustic for ZK60A, ZK60B and
some Magnesium Lithium alloys, as dimensional losses due to etching may occur.
Extended exposure of the developed coating to elevated operating temperatures
in excess of 150ºF will dehydrate the coating resulting in reduced corrosion
Powdered chemical compound comes packed in 1-gallon can to be dissolved
in 4-gallons of water.