1、f - 13 November 1984 SUPERSEDING MIL-C-20218E 14 June 1968 (See 6.4) MILITARY SPECIFICATION CHROMIUM PLATING, ELECTRODEPOSITED, POROUS This specification is approved for use by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification covers porous, electrodep
2、osited chromium plating applied to surfaces where a lubricating film raust be sustained such as cylinder bores. 1.2 Ciassification. Unless a specific type of porosity is specified (see 6.2.1), porous chromium plating may be one or more of the following types. Type1 -Channel Type II - Pin point .Type
3、 III - Intermediate Type V - Macro channel 2. APPLICABLE WCUMENTS 2.1 Government documents. 2.1.1 Specification and standard. Unless otherwise specified, the following specification and standard of the issue listed in that issue of the Department of Defense Index of Specifications and Standards (DoD
4、ISS) specified in the solicitation form a part of this specification to the extent specified herein. SPECIFICATION MILITARY MIL-S-5002 - Surfaces Treatments and Inorganic Coatings for Metal Surfaces of Weapons Systems. Beneficial comments (recommendations, additions, deletions) and any pertinent dat
5、a *ich may be of use in improving this document should be addressed to: Commander, Naval Sea Systems Command, SEA 5523, Department of the Navy, Washington, DC 20362 by using the self-addressed Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by le
6、tter. ( NO DELIVERABLE DATA REQUIRED BY THIS DOCUMENT AREA MFET THIS WCUMENT CONTAINS 21 PAGES - - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STANDARD MILITARY MIL-STD-105 - Sampling Procedures and Tables for Inspection by Attributes. (Copies of
7、 specification and standard required by contractors in connection with specific acquisition functions should be obtained from the contracting activity or as directed by the contracting officer,) 2.2 Order of precedence. In the event of a conflict between the text of this specification and the refere
8、nces cited herein, the text of this specifi- cation shall take precedence. 3. REQUIREMENTS 3.1 Materials. The materials used shall be such as to produce platings which meet the requirements of this specification. 3.2 General requirements. 3.2.1 Higher strength steel parts. Unless otherwise specified
9、 (see 6.2.1), steel parts having an ultimate tensile strength greater than 240 kilopounds per square inch (ksi) shall not be plated without specific approval of the contracting activity. 3.2.2 Stress relief treatment. Steel parts having an ultimate tensile -I strength of 150 ksi and above, which are
10、 machined, ground, cold formed or cold straightened, shall be baked at 375 2 25 degrees Fahrenheit (OF) for 3 hours or more prior to cleaning and plating for the relief of damaging residual tensile stresses , 3.2.3 Cleaning. Unless otherwise specified (see 6.2.1), steel parts shall be cleaned in acc
11、ordance with MIL-S-5002 with the exception that the control limits for tensile strength shall be in accordance with 3.2.1 and 3-2.2. the substrate and shall not interfere with adhesion of the deposit. Other basis metals shall be cleaned by methods which shall not damage 3.2.4 Plating application. Un
12、less otherwise specified (see 6.2.1), 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. 3.2.5 Plating process. The deposition of chromium shall be out of a ch
13、romic acid bath. It shall operate under conditions that shall produce a satisfactory bond between basis metal and the coating and produce porosity meeting this specification. 3.2.6 Plating thickness. The minimum radial thickness of chromium shall be 0.005 inch and the maximum radial thickness shall
14、be 0.018 inch at any location on surface. 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-c 3.2.7 Electrodeposited alloy undercoating. Electrodeposited alloy undercoating system shall be as specified provided its thickness does not exceed 0.062 inc
15、h for ordinary strength steel and 0.026 inch for high strength steel (see 3.2.2) and 0.5 inch for cast iron (see 6.2.1). The porous chromium plating electrodeposited over the undercoat shall comply with all the require- ments specified herein. 3.2.8 Embrittlement relief. Coated steel parts having a
16、tensile strength of 160 ksi and higher shall be baked within 30 minutes after plating at 375 2 25F in accordance with the following schedule: Minimum baking times Tensile strength ksi 160 - 180 180 - 220 220 and above Time (at temperature) hours 3 8 12 3.2.9 Coverage. The area to be plated shall be
17、specified (see 6.2.1). The plating shall cover the entire area specified. 3.2.10 Boundaries. Unless otherwise specified (see 6.2.1), basis metal locations where sharp edges would be conducive to premature loss of adhesion or difficulty in throwing plating shall be rounded to at least 0.031-inch radi
18、us. - 3.3 Detail requirements. 3.3.1 Porosity. 3.3.1.1 Percent porosity. Unless otherwise specfied (see 6.2.1), the surface of the chromium after finishing shall have between 15 and 35 percent porosity over the area swept when tested in accordance with 4.2.2. 3.3.1.2 Porosity deviation. In any 2 inc
19、h square, where the average porosity is between 15 and 35 percent, an area 0.5 inch or less in diameter having porosity of less than 15 percent or greater than 35 percent but not exceeding 70 percent is acceptable unless otherwise specified (see 6.2.1). When the specified range of porosity includes
20、percentages greater than 35 percent, then in any 2 inch square a portion thereof not exceeding 0.5 inch in diameter may have a percentage of porosity up to, but not exceeding 75 percent. 3.3.2 Types of porosity. Porosity shall be induced by electrochemical methods. 3.3.2.1 Channel. Type I chromium p
21、lating shall be in accordance with the characteristic network of channel type of surface porosity as shown on figures 1 through 3, inclusive. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- MIL-C-2021F MF = 9906 0420739 b 3.3.2.2 Pin point. Type II
22、chromium plating shall be in accordance with the characteristic pin point type of surface porosity as shown on figures 4 through 6, inclusive. 3.3.2.3 Intermediate. Type III chromium plating shall be in accordance with the characteristic structure between that of the channel and pin point type of su
23、rface porosity as shown on figures 7 through 9, inclusive. 3.3.2.4 Macro channel. Type V chromium plating shall be in accordance with the characteristic surface porosity as shown on figures 10 through 12, inclusive. 3.3.3 Plateaus. 3.3.3.1 Type I, channel. The average plateau size shall be not more
24、than 0.035 inch equivalent diameter, when tested in accordance with 4.2.2. 3.3.3.2 Type V, macro channel. The average plateau size shall not be smaller than 0.003 inch nor larger than 0.007 inch when tested in accordance with 4.2.2 and as shown on figure 13. 3.3.4 Pitting. 3.3.4.1 Pits or unplated a
25、reas up to 0.062 inch in diameter, surrounded by an acceptable deposit of chromium, may be present in any number provided that in any 1 square inch (in2), the porosity including pits is not greater than 40 percent. 3.3.4.2 Pits or unplated areas 0.062 inch and greater in diameter, but not exceeding
26、0.125 inch in diameter at the finished surface, surrounded by an acceptable deposit of chromium, may be present provided there are not more than three in any 1 in2. 3.3.4.3 Pits or unplated areas greater than 0.125 inch diameter, but not exceeing 0.25 inch in diameter, measured at the finished surfa
27、ce outside the area swept by the compression rings, shall be acceptable provided there are not more than five such pits or unplated areas and that there are at least 4 inches of acceptable chromium plate between any two pits. 3.3.5 Final dimensions. After the final plating and finishing operation, d
28、imensions shall be taken with a micrometer, and shall conform to dimensions specified in the applicable equipment drawing. The porous chromium plating mag be finished to final size by grinding, lapping, honing or such other mathod, provided the degree of smoothness produced by the finishing process
29、conforms to the applicable requirements of the equipment drawings. 3.3.6 Cleanliness. No loose particles of honing grit, chromium or other foreign matter shall be present. 3.3.7 Adhesion. The plating shall demonstrate good adhesion by its capability to withstand the necessary grinding/honing operati
30、ons for final dimensions. 4 y- L .- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.3.8 Workmanship. 3.3.8.1 Basis metal. The basis metal shall be free from visible defects that will be detrimental to the appearance or protective value of the plati
31、ng. The basis metal shall be subjected to such cleaning and plating procedures as necessary to yield deposits specified herein. 3.3.8.2 Plating. The plating shall be smooth, fine grained, adherent, uniform in appearance, free from blisters, pits, nodules, excessive edge build-up and other defects ex
32、cept as specified herein. The plating shall show no indication of contamination or improper operation of equipment used to produce the deposit, such as excessively powdered or darkened plating, buildup and other defects. Superficial staining which has been demonstrated as resulting from rinsing or s
33、light discoloration resulting from baking operations to relieve embrittlement, as specified (see 3.2.8), shall not be cause for rejection. 4. QUALITY ASSURANCE PROVISIONS 4.1 Responsibility for inspection. Unless otherw3.se specified in the contract or purchase order, the contractor is responsible f
34、or the performance of all inspection requirements as specified herein. specified in the contract or purchase order, the contractor may use his om or any other facilities suitable for the performance of the inspection require- ments specified herein, unless disapproved by the Government. reserves the
35、 right to perform any of the inspections set forth in the specifi- cation where such inspections are deemed necessary to assure supplies and services conform to prescribed requirements. Except as otherwise The Government r 4.2. Inspection. Each chromium plated part shall be inspected employing auch
36、mounting, illumination, optical and mechanical instruments as are necessary to facilitate examination and to verify compliance with the technical require- ments specified herein. ments specified herein shall be rejected. plating may be replated provided all the chromium is completely removed prior t
37、o replating and the removal process employed has no deleterious effect on the part Any part which fails to conform tu any of the require- Any part: rejected because of defective 4.2.1 Examination. Each part shall be visually and dimensionally examined to determine the extent to which the chromium pl
38、ating is in accordance with 3.2.6, 3.2.7, 3.2.9, 3.2.10, 3.3.4, 3.3.5, 3.3.6, 3.3.7 and 3.3.8. The examination shall be conducted also to assure freedom from defects and nonconforming quality characteristics in accordance with table I and MIL-STD-105. 5 , T Provided by IHSNot for ResaleNo reproducti
39、on or networking permitted without license from IHS-,-,-Categories Critical: Major: 101 102 103 104 105 106 107 108 109 110 111 112 Minor : TABLE I. Classification of defects. Defects None defined. Porosity type not as specified (channel, pin point, intermediate, macro channel). Electrodeposited coa
40、ting nonconforming: porosity not within percentage range, materials used in the plating process not suitable for the applicable item: coating not homogeneous or uniform in appearance, not free from nodules or blisters, evidence of %ilky“ or “burnt“ areas, excessive pitting, excessive “tree rooting“.
41、 Evidence of improper bond with basis metal. Radial thickness of plating less than the allowable minimum. Surface not finish honed, lapped or ground; not suitably smooth; not free from toolmarks, gouges, chatter marks or areas “not cleaned up“ at the final finishing operations. Plating not covering
42、the area specified, Edges not properly rounded at ports and ends; excessive edge buildup; surfaces not free of burrs. Dimensions not within requirements of the approved equipment drawings. Unplated surfaces of part nicked, gouged, galled or not free of plating deposits. Evidence of inadequate cleani
43、ng; surface voids not free of abrasive or loose material. Evidence of improper removal of defective plating (during rework) having a deleterious effect (when applicable) . Unauthorized use of electrodeposited alloy undercoating. None defined, 6 . Provided by IHSNot for ResaleNo reproduction or netwo
44、rking permitted without license from IHS-,-,-MIL-C-20218F 4.2.2 Porosity. Each part shall be examined microscopically at 50X diameters magnification and compared with photomicrographic standards as shown on figures 1 through 12, inclusive, to determine: (a) whether or not the surface porosity of the
45、 plating conforms to the percent porosity, type of porosity, pit size and quantity, and plateau size in accordance with 3.3.3.1 and as shown on figure 13; and (b) when applicable, that the observed porosity is within the range specified in the contract, order or applicable equipment drawings. 4.2.3
46、Test for cleanliness of plating. Strips of pressure sensitive tape, approximately 23nches by 3/4 inch shall be applied to representative areas of the surface. adhering to the tape. Upon removal, there shall be no evidence of particles 5. PACKAGING This section is not: applicable to this specificatio
47、n. 6. NOTES 6.1 Intended use. Electrodeposited chromium plating, covered in this specification, is intended for use on surfaces where a lubricating film must be sustained. 6.2 Ordering data. 6.2.1 Acquisition requirements. Acquisition documents should specify the following: f- Title, number and date
48、 of this specification. Whether a specific type is required (see 1.2). Permission to plate parts over 240 ksi tensile strength Method of cleaning of steel, if other than specified (see 3.2.3). If plating application is other than specified (see 3.2.4). Undercoating system, composition and thickness
49、(see 3.2.7). Area to be plated (see 3.2.9). Instances where rounding of edges is prohibited (see 3.2.10). An alternative limiting range of porosity when required (see If porosity deviation is other than specified (see 3.3.1.2). (see 3.2.1). 3.3.1. i). 6.2.2 The manufacturer of the basis metal parts should provide the plating facility with the following data: (a) (b) Strength level of steel parts (see 3.2.1 and 3.2.2). Heat treatment for stress relief, whether
