1、AECMA PRENZL32 A2 m LOL2311i 000220 2 A.E.C.M.A. STANDARD prEN2132 NORME A.E.C.M.A. Edition 1 January 1982 A. E.C.M.A. NORM ENGLISH VERSION ELECTRODEPOSITION OF CHROM1 UM FOR ENGINEERING PURPOSES AEROSPACE SERIES DEPOT ELECTROLYTIQUE DE CHROME LUFT- UND RAUMFAHRT POUR USAGES Ml%ANIQUES SERIE AEROSPA
2、TIALE GALVANISCHE METALLABSCHEIDUNG VON CHROM FR TECHNISCHE ZWECKE This industrial standard for the aerospace sector has been drawn up under the responsibility of AECMA (Association Europenne des Construteurs de Matriel Arospatial). It is published on yell0 w paper in three equivalent versions (Engl
3、ish, French, German). It will be submitted to CEN (European Committee for Standardizatibn) as a draft European Standard. Approved by The equivalent wrsionc in French end German languages -_ iDEEMALISATlC)N can be supplied by B.N.A.E., 8, rue Moreau-Vauthier of A.E.C.M.A. 1981-03-30 92100 BOULOGNE-BI
4、LLANCOURT - FRANCE. i - AECMA PREN2132 82 m 10123LB O002221 LI m lp. prEN2132 Page 2 CONTENTS 1 2 3 4 5 6 7 8 9 10 11 SCOPE FIELD OF APPLICATION REFERENCES DEFINITIONS INFORMATION TO BE GIVEN TO THE PLATER THICKNESS OF PLATED COATING CONDITION OF SUBSTRATE PROCESSING SEQUENCE REMOVAL OF CHROMIUM PLA
5、TE RECLAMATION OF WORN OR UNDEX-PLATED PARTS INSPECTION AND TESTING ANNEX A ANNEX B ANNEX C ANNEX D ANNEX E AECMA PREN2132 82 10L23LL O002222 b M prEN2132 Page 3 A.E.C.M.A. STANDARD . prEN2132 ELECTRODEPOSITION OF CHROMIUM FOR ENGINEERING PURPOSES SCOPE This standard specifies the chromium plating o
6、f parts made of carbon steels and alloy steels used in aerospace construction. It specifies : a) requirements for pretreatment, b) the method of electrodeposition of the chromium, c) maximum and minimum thicknesses, d) heat treatment, e) qualities required of the coating, f) methods of inspection. F
7、IELD OF APPLICATION 2.1 Chromium coatings are applied in aerospace construction for one or more of the following purposes : a) resistance to wear, b) resistance to corrosion and wear, c) the building-up of worn or over-machined parts. 2.2 Chromium plating should not normally be used on parts which b
8、e hotter than 450G in service. 2.3 When chromium plate is to be applied to steels of strength me Rm (max.) 1450 MPa which are subject to fatigue stresses in service, a treatment schedule together with inspection procedure and test results establishing its validity shall be sent to the Official Servi
9、ce (Procurement Authority)., for approval. REFERENCES EN2409, DEFINITIONS Shot peening for inducement of compreCsive surface residual stresses 4.1 Symbols Rm (max.) : Maximum value of the tensile strength specified in the standard for the steel to be treated, HV : Hardness VICKERS. 4.2 Units MPa : 1
10、 MPa = 1 MN/m2 = 1 N/mm2. 1) in preparation - AECMA PREN2132 82 1OL231lt 0002223 B :- I. Cr. r. e prEN2132 Page 4 5 INFORMATION TO BE GIVEN TO THE PLATER The following information shall be given on the drawing or orders : a) The number of this standard, b) the standard and metallurgical condition of
11、 the substrate, c) the requirements for stress relieving and shot peening. If either or both of these treatments is not required, this shall be stated, d) the surfaces to be plated, e) the minimum thickness of chromium to be dep65ited and, where undercoats are applied, the total plating thickness. A
12、 maximum thickness may be quoted if desired, especially for the building-up of worn and over-machined parts. - These dimensions shall be those of the finished surface after any grinding of the plated parts, f) .the final surface texture of the chromium e.g., “as plated“ or ground to g) the requireme
13、nts for heat-treatment after plating. If no heat-treatment = h) the composition of the plating solution, if this is not the standard one a specified texture, is required, this shall be stated, described in Annex C.l, together with the required controls. 6 THICKNESS OF PLATED COATING 6.1 For resistan
14、ce to wear only, iie. for parts that operate in a maintained environment of oil or grease The thickness required will depend on the conditions of service and shall be not less than 15 um. As a guide, 15 pm is Satisfactory against mild conditions of sliding rind 80 pm against moderately severe loadin
15、g, but under heavy loading or when abrasives are present a minimum thickness of 250 pm may be needed. The thicknesses shall not normally exceed 300 pm. O 6.2 For resistance to wear and corrosion, $.e. for parts subject-to wear in an atmospheric environment The total thickness of coating shall be not
16、 less than 50 um. The minimum thickness shall comply with clause 6.1. For more severe conditions of exposure the thickness shall be not less than 75 pm. The coating may if desired include an undercoat of nickel or bronze, or of copper with an intermediate coat of not less than 5 I.im nickel, but the
17、 thickness of the final coat of chromium shall be not less than 15 um* Nickel undercoats are preferred on steels of % (max.) 1450 MPa and resistance to severe conditions of corrosion. if necessary, on parts subjetc to fatigue, the applicability of the procedure shall be proved by prior testings. 6.3
18、 For building up worn or over-machined surfaces The minimum thicknesses shall comply with 6.1 and 6.2. Where a thickness of more than 250 um is needed to restore dimensions, a nickel undercoat may be applied and shall be machined before final chromium platingt On parts subject to heavy loading, a ni
19、ckel undercoat should be of hard or electroless nickel. AECNA PREN2132 -2 = 1012311 0002224 T - _. R (;ax.) MPa Up to and including 1100 Over i190 up to and including i450 Over 1450 up to and including 1800 Over i800 prEN2132 Page 5 7 CONDITION OF SUBSTRATE Stress relief None required 1 h at 19n bo
20、23OOC 18 h at i90 to 23OOC or for a shorter time at a higher temperature 24 h at 199 to 23OOC or for a shorter time at a higher temperature 7.1 All. plastic forming and heat-treatment operations shall have been completed prior to chromium plating, Operations of metal removal from unplated areas may
21、be done after plating. 7.2 The surface shall be free from metallurgical defects. 7.3 The surface texture shall be as smooth as possible and corners rounded. Parts on which the chromium coating is not to be ground after plating shall have an initial surface texture at least as smooth as that required
22、 for the chromium coating. Parts that are also to be cadmium plated shall be chromium plated first. 8 PROCESSING SEQUENCE 8.1 Stress relief 8.1.1 Before being plated, parts shall be stress relieved. The conditions stated in table 1 shall be used, but different conditions may be used if they have bee
23、n shown to be effective, TABLE i 8.1.2 If stress relief is given after shot peening, the temperature shall not exceed 23OoC. 8.1.3 Surface hardened parts shall be stress relieved at 130 to 150C for not less than 5 h. Shorter times at a higher temperature may be used if the resulting loss of surface
24、hardness of the substrate is acceptable AECMA PREN2132 82 W LOLZ31L O002225 L W *- . - prEN2132 Page 6 8.2 Shot peening 8.2.1 8.2.2 8.2.3 Shot peening shall be applied to the requirements stated in table 2. TABLE 2 Shot peening Up to and including 1100 Reconrraended if parts are subject to fatigue i
25、n service Over 1100 up to and including 14-50 Reconraended on all parts; escential if parts are subject ta fatigue in service Strongly recommended on all parts; are subject to fatigue in service (See clause 2.3) Over 1450 essential if parts COTE : Parts uhich are to be heated at 400 to 4izg solution
26、, it may be necessary to degrease them before returning them to the solution for etching and pIating. =-s- - - _ AECMA PREN2132 82 101231L 0002227 5 Over 1800 i.L prEN2132 Page 8 400 to 48OOC for 1 h min. (Note 2) 190 to 23OOC for 18 h min. (Note 1) 8.4.6 After having been plated, parts shall be was
27、hed thoroughly, dried and freed from any masking material. The final wash water should preferably be demineralised and should preferably be hot, but the temperature shall not exceed a value 2OoC lower than the melting point of any masking material. An initial wash in midly alkaline water, pH 8 - 10,
28、 may be given if desired. 8.5 Post-plating heat treatment 8.5.1 Guidance on the reasons for heat treatment is given in Annex D. 8.5.2 Heat treatment shall be given as soon as possible and in any case within 4 h of plating. 8.5.3 Heat treatment shall be carried out in air according to table 4. TABLE
29、4 R, (mx.) MPa Up to and including 1100 Over li00 up to and including 1450 Over 1450 up to and including 1800 For reduction of hydrogen embrittlement, (a) of unpeened parts not subject to fatigue and (b) for all peened parts No heat treatment 190 to 23OOC for 2 h min. (Note 1) 190 to 23OOC for 6 h m
30、in. (Note 1) For reduction of hydrogen embrittlernent and testoration of fatigue strength, unpeened parts only 400 to 480% for 1 h min. 400 to 480% for 1 h min. 400 to 48OC for i h min. (Note 2) MOTE 1 : Unpeened parts may be heated for a shorter time at a higher tenperature if the conditions have b
31、een shown to be effective in rechcing hydrogen embrittlenent. NOTE 2 : Seldom applicable, see Annex D. Surface hardened parts shall be heated at 130 to 15OOC for not less than 5 h,or at a higher temperature if the resulting loss of hardness of the substrate is acceptable. 9 REMOVAL OF CHROMIUM PLATE
32、 Chromium may be removed either by grinding or by the electrochemical method described in Annex E. Undercoats af copper shall be removed, but sound, adherent, thick undercoats of nickel need not be removed. AECIA PREN2132 82 10L2311 0002228 i prEN2132 Page 9 I 10 RECLAMATION OF WORN OR UNDER-PLATED
33、PARTS 10.1 Defective coatings and coatings that do not completely cover the substrate or undercoat, shall be completely removed before plating. Complete removal is recommended also in all other cases. 10.2 Crack detection of worn parts before replating may be necessary. 11 10.3 Parts made of steel R
34、, (max.) post-plating heat treatment, shall after the chromium plating has been removed, be heated at 190 to 23OOC for not less than 1 hto ensure freedom from hydrogen before they are replated. (For surface hardened parts, see clause 8.5.3). 1100 MPa which were not given a 10.4 Parts shall then be p
35、retreated and plated according to clauses 8.3 and 8.4 of this standard. Parts bearing an intact chromium coating may be replated according to clauses 8.4.4 and 8.4.5. INSPECTION AND TESTIIUG 11.1 Appearance . The chromium plating shall be lustrous, smooth, fine grained and adherent and shall be free
36、 from pits, visible cracks, blisters, pores, exfoliation, burning and excessive build up at edges. Fine crazing, superficial staining from rinsing and slight discolouratior from heat treatment shall not he a cauce for rejection. Areas not required to be plated shall show no signs of corrosion or che
37、mical attack and unless otherwise agreed, shall be free from chromium* 11.2 Thickness The thickness of chromium and any undercoats, on the finished parts shall be as specified on the drawing or order and shall comply with clause 6 of this standard. 11.3 Hardness The hardness of the coating shall be
38、determined. The hardness of as plated chromium shall be not less than 750 HV. Coatings heat treated in the range of 400 to 48OOC shalL have a hardness of not less than 500 HV. The hardness shall be measured under a load appropriate to the thickness of the coating. 11.4 Adhesion The appearance of the
39、 chromium plating, before and after heat treatment and/or grinding shall be as described in clause 11.2. At the discretion of the Inspection Authority destructive tests may be made e 11.5 Freedom from embrittlement The Procuring Authority or the Design Authority may require tests to be made to ensur
40、e freedom from hydrogen embrittlement. The tests may he Type Tests to establish the process and may be supplemented by periodic checks during production, AECMA PREN2132 A2 10123L1 0002229 9 ci- prEN2132 Page 10 ANNEX A METHOD FOR DETERMINING THE INTENSITY OF SHOT-PEENING A. 1 The intensity of peenin
41、g shall be measured according to EN2409 l). ANNEX B CLEANING B.l Before being plated, parts shall be cleaned to free the surface from foreign matter. The methods of cleaning chosen shall guarantee the continuity and adhesion of the chromium plate. They shall not affect dimensional tolerances or roug
42、hen the surface beyond the limit of design. They shall not alter the mechanical properties of the metal or cause hydrogen embrittlement. B.2 The following methods of cleaning are often used : B.2.1 Degreasing in solvents, in particular in chlorinated hydrocarbons, used cold or hot B.2.2 Immersion in
43、 mild alkaline cleaners with or without electric current. Cathodic current shall not be used on parts of strength R, (rnax. ) zw 1100 MPa. B.2.3 Mild abrasive blasting. B.2.4 Pickling in dilute mineral acid, preferably containing inhibitor, with or without electric current. Cathodic picklingshal not
44、 be used on steels of strength Rm (rnax. ) 1100 MPa. Plain pickling without anodic current shall not be used on steels of strength R, (rnax.) 1450 Wa. B.2.5 Anodic pickling in sulphuric acid to an appropriate national standard. Suitable processes can be used on steels of strength Rm (max. ) 1450 MPa
45、. 1) in preparation AECMA-PREN21-32 82 D LOL23Ll 0002230 5 W . *. A. -I L. Conponent prEN2132 Page 11 * Make up Conk01 ANNEX C RECOMMENDED PROCESS FOR CHROMIUM PLATING 250 g/1 C.l Plating solution 230 to 270 g/1 TABLE 5 I I Chromic acid Cr03 l I Sulphuric acid H2SO4 (d = 1,84) Ratio r03 / HSO shall
46、lie between 80/1 and 110/1 Iron plus trivalent chromium Ratio (Fe + Cr) / CrO3 less than 1/20 and preferably less than 1/40 C 2 Anodes The anodes shall be made of pure lead or preferably of lead alloyed with small quantities of antimony, tellurium, tin or silver, Internal reinforcement of anodes is
47、permitted but the reinforcing material shall not be exposed to the plating solution at any time, C, 3 Operation The temperature of th; plating solution shall lie within the range of SO to 6OoC and shall be maintained within A 2OC of the selected t emp era t ur e, The current density shall lie within
48、 the range of 30 to 100 A/dm2 and shall be maintained within they become appreciable at Rm (max.) = 1100 MPa and severe for very strong steels. Hydrogen embrittlement can be eliminated by heat treatment at 190 to 23OoC, but this treatment causes further reduction in fatigue properties. D.2 Loss in f
49、atigue strength can be avoided by adequate shot peening of the steel parts before plating. Hydrogen embrittlement can then be eliminated by heating at 190 to 23OOC and so long as the temperature of 23OOC is not exceeded, the beneficial effect of shot peening is not lost. D.3 Post-plating heat treatment in the range 400 to 48OOC eliminates hydrogen embrittlement and largely restores fatigue properties. This heat treatment can be used as an alternative to shot peening provided the mechanical properties of the steel are not affected and the reduction in ha
