Product Description:

 

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.

 

    

 

Introduction:

 

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.

 

 

Background:

 

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).

 

          

 

Process Description:

 

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”. 

 

 

Exceptions:

 

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.

 

 

Application Notes:

 

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

 

activator.

 

 

Use alkaline cleaners containing less than 2% caustic for ZK60A, ZK60B and

 

some Magnesium Lithium alloys, as dimensional losses due to etching may occur.

 

 

Limitations:

 

Extended exposure of the developed coating to elevated operating temperatures

 

in excess of 150ºF will dehydrate the coating resulting in reduced corrosion

 

protection.

 

 

Packaging/Size:

 

Powdered chemical compound comes packed in 1-gallon can to be dissolved

 

in 4-gallons of water.