1、CEN PRENs253b 92 W 3404589 0039895 T3T W Approved by COMITE DE NORMALISATION Of A.E.C.M.A. 1992-12-31 A. E.C. M.A. STAN DARD NORME A.E.C.M.A. A.E.C.M.A. NORM The equivalent versions in French and German languages can be supplied by 8.N.A.E . Technopolis 54 - 199, rue Jean-Jacques Rousseau 92138 ISSY
2、 LES MOULINEAUX CEDEX - FRANCE prEN 2536 Edition 1 December 1992 EDITE PAR LASSOCIATION EUROPEENNE DES CONSTRUCTEURS DE MATERIEL AEROSPATIAL- Technopolis - 175. rue Jean-Jacques Rousseau - F-92138 Issy-les-Moulineaux Cdex - Tl. (1) 47.36.98.76 UDC : Key words : ENGLISH VERSION Aerospace series Hard
3、anodizing of aluminium alloys Srie arospatiale Anodisation dure des alliages daluminium Luft- und Raumfahrt Hartanodisieren von Aluminiumlegierungen This .Aerospace series4 standard has been drawn up under the responsibility of AECMA (Association Europenne des Constructeurs de Matriel Arospatial). I
4、t is published on yellow paper in three equivalent versions (English, French. German). It will be submitted as a draft European Standard to CEN (European Committee for Standardization) for final vote. CEN PRENS253b 92 m 3404589 0039896 976 m prEN 2535 Page 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Co
5、ntents I Scope and field of application Purpose of process Influence and limitations of process use References Definitions Classification Information for the processor Condition of paris prior io processing Process schedule Machining after anodizing Removal of the anodic coating Required characteris
6、tics Testing Quality assurance Health, safety and environmental aspects Designation (EN PRENx2536 92 3404589 0039897 802 W prEN 2536 Page 3 1 Scope and field of application This standard specifies the hard anodizing of aluminium alloys used in aerospace construction. It shall be applicable whenever
7、referenced. 2 Purpose of process To improve : - the resistance to abrasive and erosive wear, - the electrical insulation, - the thermal insulation. To use the dimensional increase produced by the process for repair of parts out of tolerance on machining or worn in service (special case). 3 Influence
8、 and limitations of process use The anodizing produces an increase : - of the dimensions by about 50 % of the coating thickness, - of the surface roughness (factor of 1,3 to 3,0, if expressed in Ra). Anodizing results in a reduction of the fatigue strength which may reach 60 %. Shot peening before a
9、nodizing reduces the extent of this reduction. The best results as regards the properties of the anodized layer are obtained on machined surfaces ; no grinding before anodizing. Round off sharp comers. Not recommended for use on parts or items where there is a risk of retention of corrosive substanc
10、es. Avoid anodizing both faces on areas with a thickness I; 2 mm. The thickness of the anodized layer is in general : - 30 prn to 120 prn for alloys of category 1, - 30 pm to 60 pm for alloys of categoiy 2. Restrict thickness to 25 pm on the splines and threads. 4 References IS0 1463 Metallic and ox
11、ide coatings - Measurement of coating thickness - Microscopical method IS0 2106 . Anodizing of aluminium and is, alloys - Determination of mass per unit area (surface density) of anodic oxide coatings - Gravimetric method CEN PRENt253b 92 3404589 0039898 749 = PrEN 2536 Page 4 IS0 2360 IS0 2376 IS0
12、2859-1 IS0 451 6 IS0 9227 EN 2000 EN 2101 EN 2284 EN 2334 i Non-conductive coatings on non-magnetic basis metals - Measurement of coating thickness - Eddy current method Anodization (anodic oxidation) of aluminium and its alloys - Insulation check by measurement of breakdown potential Sampling proce
13、dures for inspection by attributes - Part 1 : sampling plans indexed by acceptable quality level (AQL) for lot-by-lot inspection Metallic and related coatings - Vickers and Knoop microhardness tests Corrosion tests in artificial atmospheres - Salt spray tests Aerospace series - Quality assurance - E
14、N aerospace products - Approval of the quality system of manufacturers Aerospace series - Chromic acid anodizing of aluminium and wrought aluminium alloys Aerospace series - Sulphuric acid anodizing of aluminium and wrought aluminium alloys Aerospace series - Acid chromate pickling of aluminium allo
15、ys ( FED STD 141C, Method 6192-1 : Abrasion resistance (TABER abraser) *) 5 Definitions 5.1 treated at the same time in the same bath. Batch : unless otherwise specified, it comprises parts of the same nature (form, size, material), 5.2 Pre-production parts : parts representing future production. 6
16、Classification 6.1 Types of anodizing 6.1.1 improve essentially the corrosion resistance. 6.1.2 corrosion resistance. Type A : unsealed hard anodizing. It provides the maximum wear resistance but does not Type B : sealed hard anodizing. It gives a good compromise between wear resistance and( In prep
17、aration at the date of publication of this standard. OC 20301, USA. 2, This standard is published by : Department of Defense (DODI, the Pentagon, Washington CEN PRENx253b 92 = 3404589 0039899 b85 PrEN 2536 Page 5 6.2 Categories of alloys 6.2.1 Category 1 Alloys containing less than 1 O16 of copper.
18、6.2.2 Category 2 Alloys containing between 1 % and 5 % of copper. 7 Information for the processor In addition to the designation, the following infomation shall be given : - the number of the substrate standard and the metallurgical condition of the substrate, - areas to be processed, - position of
19、elecrical contad points or alternatively areas where they are forbidden. The boundary between the masked and processed areas shall be, if possible, in an area of a geometry change. 8 The final heat treatment shall be camed out. Condition of parts prior to processing 9 Process schedule Unless otherwi
20、se specified, the sequence of operations is as follows : - masking and mounting of the parts, - cleaning, - pickling, - anodizing, - sealing, if necessary. Information concerning the individual operations is given below : 9.1 Masking may be carried out using : Masking and mounting of the parts - spe
21、cial varnishes or waxes easily removable by solvents, - plugs in suitable material, - chromic acid anodizing (EN 2101) or sulphunc acid anodizing (EN 2284), sealed and completed with wax or varnish. Generally, the anodizing is camed out over the whole surface of the part and the area intended for ha
22、rd anodizing is machined to remove the masking anodic coating. The supporting jigs shall be in aluminium alloy or titanium. They shall make effective electrical contad with the paits. CEN PRENt253b 92 = 3404589 0039900 127 m PEN 2536 Page 6 9.2 Cleaning Solvent degreasing with allowed products, foll
23、owed by alkaline cleaning is in general sufficient (see EN 2101, annex A). 9.3 Pickling Pickling operations are forbidden on parts masked by sealed anodizing without wax or varnish. The pickling shall remove the natural oxides or other contamination not eliminated by the cleaning without altering th
24、e specified characteristics. As a general rule, the pickling is done in a sulphunc-chromic bath according to EN 2334. In exceptional cases, for certain alloys in category 2, alkaline pickling may be used (see EN 2101, annex A). 9.4 Anodizing 9.4.1 Electrolyte Aqueous sulphunc acid solution with or w
25、ithout additional elements. The concentration shall not vary by more than i 1 O % from the values specified by the processor. ( The chloride content shall be less than 200 mgIl, expressed as NaCI. The aluminium content shall be less than 25 gltfor the limits of concentration chosen. The water shall
26、have a conductivity of s 1 mSlm (measured at the source of the supply). 9.4.2 Anodizing parameters The anodizing parameters (temperature, voltage, time) shall be suitable for the alloy and the composition of the bath. The treatment temperature may vary from - 20 OC to + 15 OC, depending on the proce
27、ss. The control systems shalt make it possible to ensure in a strongly and uniformly agitated bath, a tolerance of f 2 OC. ( The current used can be : - direct, - direct with superimposed alternating, - alternating, - pulsed. 9.5 Sealing When this operation is specified. it shall be camed out in wat
28、er, without or with inhibitors under the following conditions : CEN PREN+253b 92 = 3404589 0039901i Ob3 W PEN 2538 Page 7 9.5.1 Without inhibitor On making up the bath the conductivity of the water shall be less than 1 mS/m with a pH between 5.5 and 7,s (measured at the source of the supply). Sealin
29、g shall be camed out at a minimum temperature of 97 “C for at least 10 min. The bath shall be renewed when the condudivity is greater than 10 mSlm. 9.5.2 With inhibitors An inhibitor (e.g. potassium dichromate) shall be added to water with a condudivity 1 mS/m. The sealing shall be camed out at a mi
30、nimum temperature of 97 “C for at least 10 min. The pH shall be maintained between 5.5 and 6.9. The concentration of inhibitor shall be established and maintained within limits ensuring the quality defined by this standard. 10 Machining after anodizing If, for certain applications, grinding or honin
31、g is necessary, the thickness shall be chosen to take account of it. This shall be indicated in the design documents. 11 Removal of the anodic coating The treatment used shall allow to obtain a surface roughness equal to that obtained after normal surface preparation. If necessary, mechanical rework
32、ing may be canied out afler the purchasers agreement. 12 Required characteristics 12.1 - Appearance Acceptable defects : - crazing (checking of micro cracks on the surface), - showing up to the grain flow, - fissures and cavities on the microscopic scale within the anodic coating, Not acceptable def
33、ects : - irregularity of colouring on the same part, - blistering, - flaking, - burning, - pitting. CEN PREN*2536 92 = 3404589 0039902 TTT W prEN 2536 Page a Thickness of the coating (Pm) + 10 100 i 10 50 -5 12.2 Thickness It shall comply with the requirements of the design documents. 12.3 Microhard
34、ness See table 7, unless otherwise specified. Min. microhardness under 50 g load Category 2 (HV) Category 1 350 300 250 Table 1 For other thickness the microhardness value shall be agreed between the purchaser and processor. 12.4 kbrasion resistance, unsealed condition Unless otherwise specified, th
35、e max. mass losses measured on test pieces hard anodized to (50 i 5) pm (arithmetic mean of three measurements) undera load of 1000 g and 10 O00 cycles shall be : - category 1 : 20 mg corresponding to a removal of 33 pm, - category 2 : 40 mg corresponding to a removal of 7.0 prn. 12.5 Eiectrical ins
36、ulation Unless otherwise specified, the min. value of the insulation breakdown voltage measured on test pieces hard anodized io (50 i 5) pm (arithmetic mean of ten measurements) shall be : - category1 : 1200 v, - category2: 800 V. Higher values may be required when the purpose of the anodizing is th
37、at of electrical insulation. 12.6 Corrosion resistance of the sealed coating ( After 336 h min. exposure to salt spray the test pieces hard anodized to (50 f 5) pm shall not show corrosion pitting, except possibly at the electrical contact points. CEN PREN*253b 92 m 3404589 0039903 93b m prEN 2536 P
38、age 9 13 Testing 13.1 For process approval 13.1.1 Appearance Visual inspection with the naked eye. 13.1.2 Thickness In conformity with IS0 1463 or IS0 2360 or dimensional measurement on the part. 13.1.3 Microhardness In conformity with IS0 4516. 13.1.4 Abrasion resistance, unsealed condition In conf
39、ormity with FED STD 141C. Method 6192-1. 13.1.5 Electrical insulation In conformity with IS0 2376. 13.1.6 In conformity with IS0 9227. 13.2 For acceptance of parts 13.2.1 Appearance See 13.1.1. 13.2.2 Thickness See 13.1.2. 13.2.3 Other tests Other tests (see 13.1) may be camed oui by agreement betwe
40、en the purchaser and processor. Corrosion resistance of !he sealed coating 14 Quality assurance 14.1 Approval of the processor See EN 2000. CEN PREN*253b 92 = 3V04589 003990Y 72 prEN 2536 Page 10 14.2 Process approval Before beginning production, the processor shall apply the coating on pre-producti
41、on parts andlor test pieces as agreed between the purchaser and processor. All the tests required by this present standard (see 13.1) shall be carried out on these coated pre-production parts and/or test pieces, unless othewise agreed between the purchaser and processor. If the test results are sati
42、sfactory for the purchaser, he shall give his written approval to commence production. The process schedule shall not be changed thereafter without the prior agreement of the purchaser. 14.3 Accept an ce During production, the tests may be carried out on parts and/or test pieces coated under the sam
43、e condition as parts. The visual inspection (see 13.2.1) shall be performed on the whole batch, unless otheiwise specified. Unless otherwise specified, the measurement of the thickness (voir 13.2.2) shall be performed by sampling in accordance with IS0 2859-1 : - sample size code letter, table 1. sp
44、ecial inspection level S 3, - simple sampling plan for tightened inspection, - acceptance quality level (AQL) 13. The frequency and nature of the other tests (see 13.2.3) shall be determined by agreement between the purchaser and processor. 14.4 Fault sanction The parts not meeting the requirements
45、shall be rejected. After agreement of the purchaser, these parts may be reprocessed (see 11 and 9.4). 15 Health, safety and environmental aspects The locally applicable regulations and laws shall be observed. 16 Example : CEN PREN*:253b 92 34045159 0039905 709 prEN 2536 Page 11 Designation Description block Identity block Anodizing EN2 5 36A 1 -E Reference to this standard Type of anodizing (see 6.1) Alloy category (see 6.2) Thickness in vin
