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AEROSPACE MATERIAL
SPECIFICATION
AMS-QQ-C-320
juniorcollegeIssued
JUL 2000
Chromium Plating (Electrodeposited)
NOTICE
This document has been taken directly from U.S. Military Specification QQ-C-320B, Amendment 4 and contains only minor editorial and format changes required to bring it into conformance with the
publishing requirements of SAE technical standards. The initial relea of this document is intended to replace QQ-C-320B, Amendment 4. Any part numbers established by the original specification remain unchanged.
The original Military Specification was adopted as an SAE standard under the provisions of the SAE Technical Standards Board (TSB) Rules and Regulations (TSB 001) pertaining to accelerated adoption of government specifications and standards. TSB rules provide for (a) the publication of portions of unrevid government specifications and standards without connsus voting at the SAE Committee level, and (b) the u of the existing government specification or standard format.
Under Department of Defen policies and procedures, any qualification requirements and associated qualified products lists are mandatory for DOD contracts. Any requirement relating to qualified products lists (QPL ’s) has not been adopted by SAE and is not part of this SAE technical document.
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1.SCOPE AND CLASSIFICATION:
1.1Scope:
This specification covers the requirements for electrodeposited chromium plating.
1.2Classification:
1.2.1Class: Electrodeposited chromium plating shall be of the following class, as specified (e
6.2):
Class 1 - Corrosion protective plating (e 3.3.1)
Class 2 - Engineering plating (e 3.3.2)
1.2.2Finish: Class 1 plating shall be of the following types of finish, as specified (e 6.2):
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Type I - Bright finish
Type II- Satin finish
2.APPLICABLE DOCUMENTS:
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The following specifications and standards form a part of this document to the extent specified herein.
2.1U.S. Government Publications:
Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue,
Philadelphia, PA 19111-5094.
QQ-N-290Nickel Plating (Electrodeposited)
MIL-S-5000Steel, Chrome-Nickel-Molybdenum, (E4340), Bars and Reforging Stock
MIL-S-5002Surface Treatments and Inorganic Coatings for Metal Surfaces of Weapons
Systems
MIL-S-13165Shot Peening of Ferrous Parts
MIL-R-81841Rotary Flap Peening of Metal Parts
MIL-STD-105Sampling Procedures and Tables for Inspection by Attributes
MIL-STD-1312Fasteners, Test Methods --` ` , , ` ` , ` , ` , , , , , ` , ` , , ` ` , , , ` ` , , -` -` , , ` , , ` , ` , , ` ---
2.2ASTM Publications:
Available from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.
ASTM B-487Measurement of Metal and Oxide Coating Thickness by Microscopic Examination of a Cross Section
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ASTM B-499Measurement of Coating Thickness by the Magnetic Method: Nonmagnetic
Coatings on Magnetic Basis Metals
ASTM B-504Measuring the Thickness of Metallic Coatings by the Coulometric Method
ASTM B-556Thin Chromium Coatings by the Spot Test, Guideline for Measurement of
ASTM B-578Measurement of Microhardness of Electrplated Coatings
ASTM E-8Tension Testing of Metallic Materials
3.REQUIREMENTS:
3.1Materials:
The materials ud shall be such as to produce platings which meet the requirements of this
specification.
3.2General requirements:
3.2.1High tensile steel parts: Unless otherwi specified (e 6.2), steel parts having an ultimate tensile
strength greater than 240,000 psi (1655 MPa) shall not be plated without specific approval of the procuring activity.
3.2.2Stress relief treatment: All steel parts having an ultimate tensile strength of 150,000 psi
(1034 MPa) and above, which are machined, ground, cold formed or cold straightened, shall be baked at a minimum of 375 ±25°F (191 ±14°C) for three hours or more prior to cleaning and plating for the relief of damaging residual tensile stress. When peening is required (e 3.3.2.3 and
3.3.2.5), thermal stress relief shall be performed prior to shot or rotary flap peening.
3.2.3Cleaning: Unless otherwi specified (e 6.2), all steel parts shall be cleaned in accordance with
MIL-S-5002. Other basis metals shall be cleaned by methods which shall not damage the尚艺
substrate and shall not interfere with adhesion of the deposit.
3.2.4Plating application: Unless otherwi specified (e 6.2), the plating shall be applied after all basis
metal heat treatments and mechanical operations, such as machining, brazing, welding, forming and perforating of the article, have been completed.
3.2.5Underplating: Unless otherwi specified (e 6.2), class 1 plating shall be applied over an
intermediate plating of nickel in accordance with QQ-N-290 on steel, zinc and zinc-bad alloys or copper and copper-bad alloys. Unless otherwi specified (e 6.2), class 2 plating shall be
deposited on the basis metal without a preliminary plating of another metal. In no ca shall any underplate be substituted for any part of the specified chromium thickness.--` ` , , ` ` , ` , ` , , , , , ` , ` , , ` ` , , , ` ` , , -` -` , , ` , , ` , ` , , ` ---
3.2.6
Embrittlement relief: All coated steel parts having an ultimate tensile strength of 160 ksi and higher (or Rockwell hardness C36 and higher) shall be baked at 375° ± 25°F (191° ± 14 C), within four hours after plating, in accordance with the following times:
3.2.7
Coverage: Unless otherwi specified (e 6.2), the plating shall cover all surfaces including roots of threads, corners and recess.
3.2.8
Boundaries: Boundaries of class 2 plating which covers only a portion of the surface shall be free from beads, nodules, jagged edges and other irregularities.
3.2.9
Finish: For class 1 plating, the finish or luster shall be as specified (e 1.2.3 and 6.2). Type I of class 1 shall be a fully bright finish, smooth, uniform in appearance and free from frosty areas. Type
II of class 1 shall be a satin finish, smooth and uniform in appearance. Unless otherwi specified (e 6.2), either a fully bright or a dull matte finish, smooth and free from frosty areas shall be acceptable for class 2 plating finish.3.3Processing:
3.3.1
Class 1 processing: Parts for class 1 deposition shall be plated to specific dimensions as specified (e 3.4.1.1). When specified (e 6.2), parts shall be procesd in accordance with procedural instructions for form of chromium deposit (e 6.5).
3.3.2
Class 2 processing: Parts for class 2 deposition shall be plated to specific dimensions as specified (e 3.4.2.1). Unless otherwi specified (e 6.2), steel parts shall be procesd in accordance with the procedural instructions of the procuring activity as follows:
3.3.2.1
Peening: All class 2 plated parts which are designed for unlimited life under dynamic loads, shall be peened in accordance with MIL-S-13165 or MIL-R-81841 prior to plating. Unless otherwi specified
in the applicable drawings, the peening shall be accomplished on all surfaces for which the plating is required and on all immediately adjacent surfaces when they contain notches, fillets or other abrupt changes of ction size where stress will be concentrated. Plated parts which are subjected to static loads or designed for limited life under dynamic loads or combinations
thereof, need not be peened prior to plating, unless specified in the contract, order, or applicable drawing.
Minimum Baking Times
Tensile Strength
ksi Time (At Temperature)
Hours
160 - 180 3181 - 220
8221 and above
12
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3.4Detail requirements:
3.4.1Class 1:
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3.4.1.1Thickness: Unless otherwi specified (e 6.2), the minimum thickness of class 1 chromium
plating shall be 0.00001 inch or 0.01 mil (0.25 micrometre) on all visible surfaces which can be
touched by a ball 0.75 inch (19 mm) in diameter. Unless otherwi specified (e 6.2), holes,
deep recess and other openings, bas of angles, and articles with internal threads from which the external environment is completely excluded and where a controlled deposit cannot be
normally obtained shall not be subjected to a thickness requirement but shall show evidence of plating. There shall be no bare areas.
3.4.1.2Underplating: Class 1 plating is normally ud with an underplate system of nickel or copper.linearregression
Where such requirements exist (e 3.2.5), the underplate thickness shall be in accordance with QQ-
N-290. The thickness of the underplate shall not be ud in determination of the specified硕士学位英文
chromium plating thickness.
3.4.1.3Adhesion: The adhesion of the plating and any underplate shall be such that, when examined at
a magnification of approximately 4 diameters, neither the chromium plating nor any
electrodeposited underplate(s) shall show paration from the basis metal or from each other at their common interface(s) when subjected to the test described in 4.5.2. The interface between a plating and the basis metal is the surface of the basis metal before plating. The formation of
cracks in the plate or the basis metal which does not result in flaking, peeling or blistering of the plating shall not be cau for rejection.
3.4.2Class 2:
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3.4.2.1Thickness: The minimum, maximum or range of thickness for class 2 plating shall be as specified
in the contract, purcha order or on the applicable drawing (e 6.2). If a thickness is not
specified, the minimum thickness for the finished part shall be 0.002 inch or 2 mils (51 µm). The thickness requirement for class 2 plating shall apply after all metal finishing and post-plating
grinding operations have been completed.
3.4.2.2Adhesion: The adhesion of the plating and any underplate shall be such that when examined at a
magnification of approximately 4 diameters, neither the plating, nor any electrodepositedtoothfairy
underplate shall show paration from the basis metal or from each other at their common
interface(s) when subjected to the test described in 4.5.2. The interface between a plating and the basis metal is the surface of the basis metal before plating. The formation of cracks in the
basis metal or the plate which do not result in flaking, peeling or blistering of the plate shall not be cau for rejection.
3.4.2.3Hardness: The minimum hardness of a cross-ction class 2 plating, when subjected to the
microhardness test detailed in 4.5.3, shall be 600 Vickers Hardness Number (VHN) or equivalent if the plating is finished to a mi-bright or matte luster (e 3.2.9). If the plating is finished to a bright or bright pebbly luster, the minimum hardness shall be 850 Vickers Hardness Number
(VHN) or equivalent.--` ` , , ` ` , ` , ` , , , , , ` , ` , , ` ` , , , ` ` , , -` -` , , ` , , ` , ` , , ` ---
