In-Process Inspection

TM 750-245-4

piece shall be determined from the difference of the two

b. Generally, magnesium castings which have

measurements.

been formerly sandblasted, are pickled or treated with a

sulfuric or nitric-acid solution.

Treatment should

c. Other Tests. Treated pieces shall be tested for

continue until 0.002-inch surface is removed, if

conformance with any special requirements specified in

dimensional requirements permit.

the drawing. The tests shall be performed according to

the methods specified therein.

c. Old paint coatings are usually removed by use

of (caustic) liquid paint remover. This operation should

d. Rejection.

be followed by a wash or rinse to thoroughly remove and

(1) In the event unsatisfactory quality is

neutralize the alkaline.

detected in the processing treatment being used, the

d. Insure proper treatment is used as required.

inspector will promptly notify processing personnel to

The following can be used for magnesium treatments:

take necessary corrective action. All work which was

processed under doubtful conditions of the solution

(1) Chrome pickle treatment.

utilized will be rejected and reprocessed to the

(2) Dichromate treatment.

satisfaction of the inspector.

(3) Galvanic anodizing treatment.

(2) If a sample fails to conform to the

(4) Chromic acid brush-on treatment.

requirements of this document, all items being

(5) Fluoride anodizing process plus corrosion

processed as represented by the sample will be

preventive treatment.

rejected.

Rejected items may be submitted for

(6) Chromate treatment.

acceptance after the items have been reprocessed.

Reprocessed items are subject to 100 percent

e. Random sampling for visual examination and

inspection in order to determine if defects still remain.

workmanship shall be conducted.

2-15. Magnesium-Final Inspection

f. All items exposed, to weather shall be examined

a. All equipment fabricated of magnesium will be

very closely for any evidence of corrosion or

inspected for the proper smoothness and finish.

deterioration of finish. If there is any evidence of

corrosion, the finish must be removed to bare metal and

b. Any detected bare spots will be refinished as

cleaned of any corrosion or corrosion products and

required.

finished using procedures provided.

c. Any signs of apparent contamination such as

2-14. In-Process Inspection

dirt, grease, and pits will be removed and any necessary

a. Product Examination. Samples of treated parts

actions required will be taken to correct the problem.

shall be visually examined to determine conformance to

d. Check those areas that specify special painting,

workmanship standards, quality of the treated surface,

etc.

and any other requirements specified by the system

e. Scratches which must be removed and

documentation. A visual examination of the processed

reworked and / or finished.

surface shall be made for complete and uniform

f. Coatings shall be visually examined for

coverage. Surfaces shall be examined for coloring and

continuity and uniformity.

general characteristics, described herein, particular to

g. Coatings shall be checked for dry film thickness

the type treatment being examined, which shall be an

as required by this document and / or the applicable

indication of satisfactory time of treatment and condition

system documentation. Small steel panels prepared

of solution.

with films should be used as comparators to the item

b. Dimension Change Determination.

The

being inspected.

thickness of each piece selected prior to treatment shall

h. The thickness requirement generally shall be

be determined by measuring with a micrometer which

considered met when the coating is of sufficient

reads accurately to 0.0001 inch. The pieces shall then

thickness to completely cover and impart characteristic

be processed concurrently with the remainder of the lot.

color of the coating to the surface. Generally, four mils

The pieces shall be distributed throughout the various

thickness is sufficient if a surface is completely stripped;

bitches during processing so as to be representative of

otherwise, a five mil thickness is acceptable and

the entire lot. The thickness of each piece shall be

adequate.

determined after treatment by measuring the same

location as before. The dimensional changes of each

2-4