Specification ZINC-NICKEL COATINGS WITH PASSIVATION JED ON FERROUS MATERIAL Passivation, Zn-Ni-steel

Transcription

1 Specification Class: Surface protection Class No.:50 ZINC-NICKEL COATINGS WITH PASSIVATION JED ON FERROUS MATERIAL 739 Previous Edition Part name (for databases) Passivation, Zn-Ni-steel Scope The specification refers to parts which are extremely stressed with regard to corrosion, i. e. parts which are exposed to the outdoor atmosphere (direct outdoor weathering). It is especially applicable for parts subjected to high operating temperatures above +80 C and refers to corrosion protection of parts made of ferrous materials. All coatings must be free from Hexavalent Chromium. There are the following types: JED JED JED JED JED JED JED Invalid! If JED is indicated on the drawing, JED has to be applied. Invalid! If JED is indicated on the drawing, JED has to be applied. Invalid! If JED is indicated on the drawing, JED has to be applied. followed by a sealing process, with silver coulour of the coating; followed by a sealing process, with black coulour of the coating; without sealing process, with electrical conductivity, with silver coulour of the coating; without sealing process, with electrical conductivity, with black coulour of the coating. If JED-739 is quoted in the drawing JED shall be used. Warning instruction for use Certain customers (VOLVO and SCANIA at the time of preparation of this standard) require that the release of Nickel does not exceed 0,5 µg/cm²/week (test according to EN 1811). If zinc-nickel processes are used for these customers it must consequently be guaranteed that the threshold value is kept. Thermal range of application of the parts with surface protection: -60 C to +150 C. Compiler Approved Product Group: 4961 Continuation page 2 to 5 Katarzyna Śpiewak JED.dot Template version 03 Hans Voß Doc. Code Language Rev en - G

2 JED-739 : Page 2 2 Requirements 2.1 Requirements on the substrate The parts to be electroplated shall be free form surface, treatment, or other defects adversely affecting the corrosion protection or the adhesion of the coating to the substrate. These are for instance slag inclusions, laps, score marks with a depth of more than 0.2 mm, pore clusters, sink marks, weld marks, whirls and bubbles. Parts with cracks or with material separations transversal to the force must not be used. 2.2 Requirements on the coating The parts shall have a dense and homogeneous coating. The nickel content of the coating must be 10 to 15 %. The coatings must not have any defects affecting corrosion protection, as for instance pores, cracks, roughnesses, stains or damages. The coatings must firmly adhere to the substrate and must not spall in case of slight deformation. The process conditions must be chosen in such a way that the usability of the finished part is not affected. Prior to passivation or chromating, an appropriate heat treatment to avoid hydrogen embrittlement shall be applied to parts with a strength of more than 1000 N/mm² (Corresponding hardness: 30 HRC, 295 HV, 280 HB). This also includes those parts where the strength locally exceeds 1000 N/mm² due to case hardening or cold working. The parts surface protection included shall be within the tolerances provided on the standard sheets or drawings, with special consideration given to the thread dimensions. The requirements on the corrosion protection of formed areas apply to areas formed after plating. Measuring points for the coating thickness on screws and nuts In case of screws the approximate center of the head surface or the approximate center of the end is the measuring point. This statement is based on the assumption that the coating thickness in these areas approximates that in the first turn of the thread (fig. 1 and fig. 2) for screws with a length of about 5 d. If necessary, particular agreements concerning the measuring points are to be made for screws whose length exceeds 5 d and for special parts. In case of screws with internal drive the coating thickness is measured in the center of the remaining head surface or in the center of the end (fig. 2 to fig. 5). The coating thickness on nuts is measured in the center of a wrench surface (fig. 6).

3 JED-739 : Page 3 Examples of measuring points (X): X X X X X X Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure Subsequent sealing process (JED and -4) For the purpose of sealing which increases corrosion and temperature resistance, substances with a low tendency to coat formation are placed in the wet or dry passivation or chromate coating. Only sealings which are resistant against cold degreasing agents are allowed. Sealing may considerably reduce the conductivity of the coating. If conductivity is significant for the particular case of application, sealing shall not be applied. 2.3 Coefficients of friction of threaded parts On threaded parts to be used with preformed threads in the counterpart, plating shall be carried out in such a way that In steel counterparts a total coefficient of friction µst from 0,12 to 0,18, is met, if measured according to ISO In aluminium counterparts the total coefficient of friction µal does not exceed 0,25. The actual tolerance range must be provided and agreed with WABCO Engineering, preferably the same limits as for steel should be kept. The measurement should be conducted according to ISO 16047, but: o material of nut: wrought aluminium alloy o nut free from oil or grease, no ultrasonic cleaning o hardness of aluminium nut: 90 to 110 HB (2,5/62,5) o tightening torque: 60% of VDI 2230 (for strength 8.8 and µ=0,12) To achieve these requirements lubricants can be applied as parts of the top-coat or separately. This does not apply to thread-forming screws (see JED-836 and 837). In cases where a different coefficient range is defined in the drawing, that has to be used. Uneven, rough or too thick coatings shall be avoided in the threaded area. For measuring the coefficient of friction of screws and nuts screw testing equipment shall be applied which permits a uniform slow tightening and releasing of the screwed connection.

4 JED-739 : Page Requirements on the corrosion protection Requirement until appearance of white (zinc) corrosion Test in accordance with ISO 9227, NSS test Test duration Requirement Rack parts Drum parts Formed surface areas JED a h (1) 120 h (1) no requirement without zinc corrosion, JED a h (1) 120 h (1) (2) grey haze is accepted (1) As well after heat treatment 24 h at +120 C. (2) For steel parts which have been tempered for stress relief (e.g. Crimp Ring) the requirement is 120 h Requirement until appearance of red (base metal) corrosion Test in accordance with ISO 9227, NSS test Test duration Requirement Rack parts Drum parts Formed surface areas JED-739-3, -4, h (1) 720 h (1) 720 h (1) 480 h (1, 2) 480 h (1, 2) without JED h (1) 720 h (1) 480 h (1, 2) base metal corrosion 720 h (1) 600 (3) 480 h (1, 2) (1) As well after heat treatment 24 h at +120 C. (2) Exceptional requirement for the shaft and thread area of parts with thread. (3) Exceptional requirement for steel parts which have been tempered for stress relief, (e.g. Crimp Ring). 2.5 Coating thickness In general, the required resistance is achieved with the nominal thicknesses indicated below: Parts without thread Threaded parts 10 µm 6 µm 2.6 Test for hexavalent chromium Hexavalent Chromium must not be present in the coating. The test to prove that no hexavalent chromium is present has to be done according to ISO If the concentration of hexavalent chromium is below 0,1 µg/cm² according to this test, the parts are regarded as being free from hexavalent chromium. 2.7 Resistance to media Zinc and zinc alloy coatings according to this specification are not resistant to acids and strong alkaline materials, as for instance cleansing agents. 2.8 Test of brittle fracture tendency for materials with strength > 1000 N/mm² The parts are subjected to a pre-loading test according to or similar to ISO No fracture must occur. 2.9 Test of adhesion The parts are stored 30 minutes at +220 C ± 10 C in air and immediately afterwards immersed in water with a temperature of +15 C to +25 C. No spalling or blistering of the coating may occur.

5 JED-739 : Page Colour of coating For types JED and JED the colour silver may be defined in the drawing. A slight yellow, blue or green coloration is accepted in this case. There are no requirements for the gloss. All colours can have yellow, blue or green iridescence. Identical parts from one process must have a homogeneous appearance. 3 Guarantee 3.1 General The manufacturer is obliged to prove by regular random test that the requirements specified in chapter 2 are observed, and to keep the inspection documents accessible to the customer. 3.2 Initial sample Together with each initial delivery several initial samples and the initial sample inspection report must be submitted for the inspection of dimensions and material. 3.3 Guarantee The material supplied subsequently must correspond to the released sample, to the drawings and to the requirements of this specification. 4 Document Versions Revision Date Changes Initial Version A Types JED and JED added B Types JED-739-4, JED and JED added, application of CrVI free passivations included C Inalidation of the variant -0; -1 ;-2 due to hexavalent chromium ions (Chromium VI) limits D Changes in point 2.3 coefficient of friction limits updated Requirement until appearance of corrosion in points and changed. E Requirement until appearance of corrosion in points and changed. Point 3 Guarantee added. Colours of the coatings added to the JED variants in point 1 Scope. F Error correction G Definition of significant surface by ball with 20 mm diameter removed in chapter 2.2. Technical update of 2.8