1、O O Edition approved for publication Comments should be sent within six months after the date of publication decision O O C8 Chairman CEN PRENw278b 93 3404589 00400lb 039 A.E.C.M.A. STANDARD NORME A.E.C.M.A. A.E.C.M.A. NORM prEN 2786 Edition P 1 February 1993 EDITE PAR LASSOCIATION EUROPEENNE DES CO
2、NSTRUCTEURS DE MATRIEL AROSPATIAL Technopolis - 175, rue Jean-Jacques Rousseau - F-92138 Issy-les-Moulineaux Cedex - Tl. (1) 47.36.98.76 UDC : Descriptors : Srie arospatiale Argentage lectrolytique des lments de fixation ENGLISH VERSION Aerospace series Electrolytic silver plating of fasteners Luft-
3、 und Raumfahrt Elektrolytisches Versilbern von Verbindungselementen This “Aerospace Series“ pre-standard has been drawn up under the responsibility of AECMA (Association Europenne des Constructeurs de Matriel Arospatial). It is published on green paper for the needs of AECMA-Members. It has been tec
4、hnically approved by the experts of the concerned Commission following comment by the Member countries. Subsequent to the publication of this pre-standard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identificati
5、on of the standard. After examination and signature of the AECMA Standard Checking Centre (NPS) and formal agreement of the Official Services of the Member countries it will be submitted as a draft European Standard to CEN (European Committee for Standardization) for final vote. 1993-02-26 A.E.C.M.A
6、. Technopolis - 175, rue Jean-Jacques Rousseau 921 38 Issy-les-Moulineaux Cedex - FRANCE Mr. WILLIAMS 0 aecma 1993 CEN PREN*278b 93 M 3404589 O040037 T75 prEN 2786 Page 3 1 Scope This standard specifies the electrolytic silver plating of fasteners used in aerospace construction. It shall apply whene
7、ver referenced. 2 Normative references EN 2000 Aerospace series - Quality assurance - EN aerospace products - Approval of the quality system of manufacturers EN 2828 Aerospace series - Adhesion test for metallic coatings by burnishing EN 2830 Aerospace series - Adhesion test for metallic coatings by
8、 shearing action EN 2831 EN 2832 Aerospace series - Hydrogenembrittlement of steels - Test by slow bending Aerospace series - Hydrogen embrittlement of steels - Notched specimen test 3 Purpose of process To prevent galling or seizure. 4 Technical requirement 4.1 Preparation Parts shall have chemical
9、ly and/or electrolytically clean surfaces prepared with minimum abrasion, erosion or pitting, prior to immersion in the plating solution. Treatments which may produce hydrogen embrittlement shall be avoided. After cleaning and prior to immersion in the plating solution, parts may be etched in a suit
10、able solution such as ferric chloride and/or hydrochloric acid, to promote adhesion. Electrical contact between the parts and the power source shall be established in such a manner as to ensure that neither chemical/immersion deposition nor electrical arcing or overheating will occur. 4.2 Procedure
11、The parts shall be silver plated over a suitable nickel and/or silver strike by an approved method to the thickness quoted in the product standard or in the definition document. The plated parts shall be removed from the plating solution then thoroughly rinsed and dried. Previous page is blank CEN P
12、RENx278b 93 3404589 00400L 9OL = prEN 2786 Page 4 5 Required characteristics 5.1 Appearance The silver plate shall be sound, smooth, continuous, uniform in colour and free from blisters and other imperfections (see 5.4.1 1. Abrasion of plating on corners and edges of threaded fasteners is acceptable
13、, but plate shall be continuous on the threads. Marking of the cone section of self-locking nuts, produced in off-setting the locking beams or other deformation, is acceptable. 5.2 Composition Silver as plated shall be not less than 99,9 % pure, the process of plating shall be controlled to produce
14、this purity. 5.3 Post treatments De-embrittlement is mandatory on martensitic steel where the tensile strength can exceed 1 100 MPa. De-embrittlement, where applicable, shall be carried out as soon as possible, but no later than 16 h after plating, the time and temperature are optional. Where de-emb
15、rittlement is specified, the parts or test pieces shall be tested to EN 2831 or EN 2832 or parts shall be subjected for 200 h at ambient temperature to an axial load equal to 75 % of the tensile strength of the part and must show satisfactory results. No fracture is permissible before 200 h. 5.4 Adh
16、esion To be checked on parts or test pieces. These parts or test pieces shall be heated in air to the following applicable temperature held at temperature within f 8 OC for no less than two hours and cooled in still air. (a) The temperature of any de-embrittlement shall be considered sufficient. If
17、no de-embrittlement is carded out, the temperature shall be the maximum test temperature of the parts. (b) The temperature shall be the maximum test temperature of the parts. Parts with a maximum test temperature of up to and including 425 OC : Parts with a maximum test temperature of more than 425
18、OC : 5.4.1 Adhesion requirements After heating, parts or test pieces shall be visually examined at 10 times magnification. Parts shall be free of detrimental blisters and of indications of poor bond such as flaking and lifting of the plating. Some small blisters are acceptable provided the parts mee
19、t the adherence requirements. Blisters 0,38 mm and larger in diameter, are not acceptable. After visual examination, the parts or test pieces shall be subjected to one of the following adhesion tests, EN 2828, EN 2830 or any other adhesion test that is agreed. CEN PREN*:278b 93 3404589 0040019 848 H
20、 prEN 2786 Page 5 6 Classification of tests 6.1 Acceptance tests The following tests shall be carried out on each lot : (a) Appearance (see 5.1 1 ; (b) Thickness (as defined on the product standard or definition document) to be measured by an agreed method ; (cl Adhesion (see 5.4, 5.4.1). NOTE : A l
21、ot shall be all parts of the same size and shape, made of the same alloy, plated to the same thickness in the same set of solutions within one 24 h period. 6.2 Periodic tests The following tests shall be performed at a frequency selected by the process controller : (a) Composition (see 5.2) ; (b) Post treatments (see 5.31. 7 Quality assurance EN 2000
