MIL-STD-867 Temper Etch InspectionThis standard establishes requirements and test for performing temper etch inspection of carburized steels and tool and low alloy steels, which are heat treated above 1.24 x 109 Pascal PA 1.26 x 102 kilogram - force/square millimeter Kgf/mm2 or 1.8 x 105 pound - force/square inch psi. This standard applies to aircraft and missiles structural and propulsion system components when MIL-HDBK-6870 for guidance only and/or MIL-STD-866 are reference documents in the solicitation or contract.

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STEP

PROCESS

SOLUTION

TIME

TEMPERATURE

REMARKS

1.

Nitric Acid

Etch

Hydrochloric

acid

4.0% - 6.0% (by

volume) in

alcohol or water

1 �  to 3 �

minutes

Ambient

To de-oxidize

part.  Agitate

part during

entire

immersion time

2.

Rinse

Circulating water

Rinse only

Ambient

To remove acid.

Total immersion

required.

3.

Nitric acid

Nitric acid 2.5%

to 3.5% (by

volume) in

alcohol or water

1 �  to 2 �

minutes

Ambient

Agitate parts

during entire

immersion time.

Exact time may

vary to produce

desired black

oxide film.

4.

Rinse

Circulating water

Rinse only

Ambient

To remove acid.

Total immersion

required.

5.

Hydrochloric

acid. Acid dip.

Hydrochloric

acid

4.0% - 6.0% (by

volume) in

alcohol or water

1 �  to 3 �

minutes

Ambient

Agitate parts

during entire

immersion time.

To remove

black oxide film

and produce a

uniform

brownish/gray

surface.

6.

Rinse

Circulating water

Rinse only

Ambient

Agitate parts

when immersed

7.

Neutralize

Any alkali

solution with pH

of 10 minutes

15 seconds

minimum

Ambient

Agitate parts

when immersed

8.

Rinse

Running water

Rinse only

Ambient

To remove

caustic

*9.

Rinse

Alcohol

Rinse only

Ambient

To remove

water

10.

Inspect and evaluate per appropriate criteria.

**11.

Oil

Rust

preventative oil

Dip only

Ambient

To prevent

corrosion.

* Optional procedure: Hot water rinse (66°C minimum {150°F}), followed by a dry air blast may be used in lieu of this rinse.

If a hot water rinse is used in lieu of the alcohol rinse, the rinse in Step 8 may be omitted.

Pre-cleaning, water rinse and Steps 1 thru 10 shall be one continuous operation.

** Apply the oil after the required embrittlement relief bake.  This step may be omitted if the facility can show

evidence that corrosion during the queue between process steps is not an issue.  This could be the case in

a low humidity environment.

Maintain all rinses at less than or equal to 350 ppm dissolved solids.