标准施工手册 STANDARD PRACTICES MANUAL 20-00-02/70-00-01(72)

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Silver plating types:
Type I - Matte  Deposits without luster comparable to those normally obtained from silver-cyanide plating solutions operated with brighteners.
Type II - Semi-bright  Semi-lustrous deposits comparable to those normally obtained from silver-cyanide plating solutions operated with brighteners.
Type III - Bright  Sometimes obtained by polishing or by use of brightener.
Silver plating grades:
Grade A  With supplementary tarnish-resistant treatment (chromate treated).
Grade B  Without supplementary tarnish-resistant treatment.
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(1) Prepare surfaces.
WARNING: USE CORRECT PERSONAL PROTECTION.  PROCEDURES THAT NEED GRIND/MACHINE WORK WILL CAUSE LOOSE PARTICLES THAT CAN GET IN YOUR EYES.
(a)  
Grind or machine diameter or surface to be silver-plated, not to exceed dimensions specified in applicable manual for part being repaired.

(b)  
After grinding or machining operation, surface finish shall be 80 microinches (2,032 micrometers) or better. Dimensions shall allow for plating thickness specified in applicable manual or as indicated in the note at the beginning of this procedure.

(c)  
Perform fluorescent penetrant or magnetic particle inspection (SECTION III), as specified for part being plated, to ensure that grinding or machining operation has caused no surface cracks. No cracks are permissible.

(d)  
Degrease, clean, and apply solutions to part in accordance with Federal Specification QQ-S-365B.

(e)
Mask all surfaces of part that are not to be plated.

(2) Apply silver plate.
CAUTION: WHEN THE BASE METAL IS ROCKWELL C40 OR HARDER, THE PART SHALL BE STRESS-RELIEVED AT 300F (149C) FOR TWO HOURS PRIOR TO PLATING.
(a)  
Apply silver plating to surfaces of part in accordance with Federal Specification QQ-S-365B, to obtain specified dimensions.

CAUTION: WHEN THE BASE METAL IS ROCKWELL C40 OR HARDER, THE PART SHALL BE HYDROGEN-EMBRITTLEMENT-RELIEVED WITHIN FOUR HOURS AFTER PLATING.

(b)  
If required in accordance with applicable manual, relieve silver plating on parts with Rockwell C40-54 hardness for three hours at 365 to 385F (185 to 196C). Relieve silver plating on parts with Rockwell C55 and harder for five hours at 265 to 285F (129 to 141C).

(c)  
Visually inspect plating for quality, coating thickness, roughness, adhesion, and solderability in accordance with Federal Specification QQ-S-365B.

(d)  
Store silver plated part in a container that will prevent entrance of sulphur-bearing atmosphere.

I.  Method No. 403I: Electroless Nickel Plating
Parts not meeting manual limits may be processed to size using electroless nickel plate in accordance with MIL-C-26074/EMS52404, type and class as applicable.
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CAUTION: DUE TO MASKING PROBLEMS, IN MANY CASES ELECTROLESS NICKEL PLATE IS NOT THE MOST DESIRABLE REPAIR METHOD.  MASKING SHOULD BE CONSIDERED FIRST.
(1)  
As necessary, grind the nonconforming surface to prepare for electroless nickel plate, allowing 0.0002 inch minimum and up to 0.0050 inch maximum thickness of plating per surface. Maintain balance of requirement and hold stock removal uniform to facilitate plating.

NOTE:  Nickel plate may be applied in thickness of 0.0002 to 0.0050 inch per surface. However, thickness of over 0.0005 inch may require additional machining to obtain required size and/or finish.  Surfaces to be plated to size must meet all manual requirements except dimensional, prior to plating.

(2)  
Visually inspect.

(3)  
Mask as required and electroless nickel plate the surface prepared to required size.

NOTE:  Pre- and post-baking requirements shall be in accordance with the applicable plating specification.
　
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