1、 ENGINEERING MATERIAL SPECIFICATION Date Action Revisions Rev 05 2016 03 22 Revised Removed A2 G. Weber, NA 2015 06 19 N Status A1/A3 to N Status replace with WSS-M21P51-A2. G. Weber, NA 2004 09 14 Revised Para 3.5.1 revised D. Drobnich 2004 09 02 Activated D. Drobnich Controlled document at www.MAT
2、S Copyright 2016, Ford Global Technologies, LLC Page 1 of 5 CORROSION PROTECTIVE COATING, ZINC NICKEL ALLOY, WSS-M21P44-A1 TRIVALENT PASSIVATE, SILVER NOT TO BE USED FOR NEW DESIGN CORROSION PROTECTIVE COATING, ZINC NICKEL ALLOY, WSS-M21P44-A3 TRIVALENT PASSIVATE WITH CATHODIC ELECTROCOAT, BLACK NOT
3、 TO BE USED FOR NEW DESIGN 1. SCOPE The materials defined by these specifications are corrosion protective coatings applied sequentially per supplier specifications over steel. They consist of an alkaline zinc nickel alloy electrodeposit and a trivalent chromium passivate/adhesion promoter. A3 is fo
4、llowed respectively by an organic seal, a cathodic electrocoat, or a waterborne top coat. When used with an integrally cured torque modified post dip, these processes provide consistent torque-tension control. All processes are free of hexavalent chromium, lead and cadmium. 2. APPLICATION These spec
5、ifications were released for materials used as corrosion protective coatings over steel fasteners and small parts. The processes may induce hydrogen embrittlement and therefore these coatings must be hydrogen embrittlement relieved when applied to high hardness parts in accordance with WSS-M99A3-A.
6、The cure temperature of the cathodic system for A3 is 175 to 200 C. These coatings shall not be specified if this temperature adversely affects the component being coated. 2.1 SERVICE TEMPERATURE The maximum continuous service temperature for A1 is 310 C. The maximum continuous service temperature f
7、or A3 is 260 C. 3. REQUIREMENTS 3.1 STANDARD REQUIREMENTS FOR PRODUCTION MATERIALS Material suppliers and part producers must conform to the Companys Quality System Requirements for Production Materials (WSS-M99P1111-A). Part producers must use approved materials specified on the Companys Approved S
8、ource List. 3.2 APPROVED APPLICATOR QUALITY REQUIREMENTS Applicators must follow coating manufacturer procedures and recommendations for chemical usage, equipment, analysis and processing. 3.3 APPEARANCE ENGINEERING MATERIAL SPECIFICATION WSS-M21P44-A1/A3 Copyright 2016, Ford Global Technologies, LL
9、C Page 2 of 5 3.3.1 The ZnNi coating will have a metallic silver appearance prior to passivate/adhesion promoter application. 3.3.2 The passivate/adhesion promoter will have an appearance of slight iridescence and color variation consistent with interference films (e.g. yellow, orange, green, blue,
10、purple variegation). 3.3.3 The cathodic coating used for A3 will be a semi-gloss black finish free from discontinuities. The gloss level for A3 shall be 25 to 55 of gloss when measured using a 60 meter. 3.4 COATING COMPOSITION 3.4.1 The alkaline ZnNi electrodeposit shall have a nickel content of 12
11、to 15% as measured by calibrated X-ray fluorescence spectrometers in accordance with the suppliers requirements. In some instances a strike layer may be applied to the substrate prior to ZnNi electrodeposition. In such cases the presence of a strike layer must be noted so that appropriate methods fo
12、r measuring composition and thickness of the ZnNi may be employed. 3.4.2 The alkaline ZnNi electrodeposit shall have a phase composition which includes substantial metallurgical gamma phase ZnNi as defined by standard reference phase diagrams such as ASM Handbook, Volume 3, 10th edition. Presence of
13、 substantial gamma phase ZnNi may be demonstrated by comparing x-ray diffraction patterns to reference materials such as ICDD PDF 06-0653. Crystallographic preferred orientations, such as 330 and/or 600 Miller index hkl for gamma phase ZnNi, should be present in accordance with the chemical supplier
14、s requirements; and subject to periodic verification using x-ray diffraction or an alternative, preapproved, standard crystallographic determination method. 3.4.3 The passivate/adhesion promoter shall have a composition in accordance with the chemical suppliers requirements. For A3, the passivate/ad
15、hesion promoter must be cobalt and carboxylic acid free. 3.4.4 The cathodic coating of A3 shall have a composition in accordance with the chemical suppliers requirements. 3.5 COATING THICKNESS 3.5.1 The ZnNi electrodeposit will have an optimum thickness of 8 + 4/- 2 microns measured on flat surfaces
16、. Documentation demonstrating throwing power, measured in accordance with suppliers instructions, in excess of 70% will assure adequate thickness in recessed areas including threads. 3.5.2 The passivate/adhesion promoter thickness is not subject to measurement but will be less than one micron and gr
17、eater than 50 nm based upon SEM examinations using cryofractured samples and/or calibrated depth profiling using scanning Auger or x-ray photoelectron spectroscopies. 3.5.3 A specific cathodic coating thickness for A3 is not specified. The minimum thickness shall be sufficient to meet the corrosion
18、requirements of the substrate material. A typical film that exhibits the appropriate corrosion resistance for A3 is 12.7 to 20.0 microns in thickness. 3.5.4 Excessive coating thickness on threaded components may cause assembly concerns. The general requirements of the Ford Worldwide Fastener Standar
19、ds, Finish Specification WX100, and Section 5 apply to these coatings. ENGINEERING MATERIAL SPECIFICATION WSS-M21P44-A1/A3 Copyright 2016, Ford Global Technologies, LLC Page 3 of 5 3.6 THREAD ACCEPTANCE REQUIREMENTS (WA900, WE900, WX100) For thread acceptance requirements see Ford Worldwide Fastener
20、 Standards WA900, WE900 and WX100. 3.7 CURING AND TRANSPORTATION 3.7.1 The ZnNi electrodeposit with passivate/adhesion promoter will be cured and packaged in accordance with suppliers requirements prior to transportation to a subsequent coating applicator. 3.7.2 The cathodic electrocoat for A3 shall
21、 be cured 20 minutes at a metal temperature of 175 to 200 C. 3.7.3 These coatings shall not be used on materials that are adversely affected by these metal temperatures. 3.8 CLEANING Prior to coating, the substrate shall be free of oil, dirt, and similar foreign materials. If a cleaning process is n
22、ecessary, it shall have no detrimental effect on the substrate, including freedom from embrittlement. 3.9 ADHESION The coating shall withstand normal handling, storage, and installation without flaking or peeling or other loss of adhesion. 3.10 TORQUE TENSION (WZ101) Applicators preparing the final
23、layer of parts in accordance with A3 must have torque tension measurement equipment in accordance with WZ 101. The coatings shall meet the torque and friction coefficient specified in Table 1. 3.11 RESISTANCE PROPERTIES 3.11.1 Corrosion resistance (SAE/USCAR-1, ASTM B 117, ASTM D 610, WX100) Fastene
24、rs shall be tested and evaluated in accordance with SAE/USCAR-1, and shall pass the number of hours specified in Table 1 and the “General Requirements” of WX100. Parts other than fasteners shall be tested in accordance with ASTM B 117. Parts shall show no single ferrous corrosion spot larger than 1.
25、5 mm in diameter, and shall not exhibit ferrous corrosion overall exceeding 0.1%, per ASTM D 610, grade 8, after the number of test hours specified in Table 1. 3.11.2 Water Resistance (FLTM Bl 104-01) Shall not blister or show any signs of red rust when subjected to immersion in water for 240 hours.
26、 ENGINEERING MATERIAL SPECIFICATION WSS-M21P44-A1/A3 Copyright 2016, Ford Global Technologies, LLC Page 4 of 5 3.11.3 Gasoline Resistance Shall not blister or show any signs of softening or dulling when subjected to immersion in current factory fill gasoline for 24 hours at 23 +/- 2 C. 3.11.4 Hot Oi
27、l Resistance Shall not blister or show any signs of softening or dulling when subjected to immersion in engine oil (SAE 10W30 per WSE-M2C903-A2 or equivalent) for 24 hours at 66 +/- 3 C. 3.11.5 Ethylene Glycol Resistance Shall not blister or show any signs of softening or dulling when subjected to i
28、mmersion in a 50% solution of water and long life coolant concentrate (WSE-M97B44-B or equivalent) for 24 hours at 23 +/-2 C. 3.11.6 Brake Fluid Resistance Shall not blister or show any signs of softening or dulling when subjected to immersion in currently approved brake fluid for 24 hours at 23 +/-
29、2 C. 3.11.7 Power Steering/Transmission Fluid Shall not blister or show any signs of softening or dulling when subjected to immersion in current factory fill power steering and transmission fluid for 24 hours at 66 +/-3 C. 3.12 ELECTRICAL CONDUCTIVITY Coating system A exhibits electrical continuity
30、to the substrate but not sufficient enough to be considered acceptable for general for electrical grounding applications. Coating systems A3 and are not recommended for electrical grounding applications. 3.13 FORMABILITY For A1, parts such as brackets, stampings, tubing, etc. that will be post forme
31、d following processing shall follow coating manufacturers approved procedures; such as, ISO 8401-1986 (E) - cylindrical mandrel bending ensuring bendability, must be used and results recorded. 3.14 ULTRAVIOLET EXPOSURE (ASTM D 4587-01, ASTM G 154-00a) A1 coating systems are recommended for applicati
32、ons using ASTM D4587-01. A3 coating system is recommended for applications using ASTM G154-00a. ENGINEERING MATERIAL SPECIFICATION WSS-M21P44-A1/A3 Copyright 2016, Ford Global Technologies, LLC Page 5 of 5 TABLE 1 GUIDANCE TO PROPERTIES OF WSS-M21P44-A1/A3 COATING SYSTEMS Specification Color Typical
33、 Thickness m WZ 101 Torque NM (a) WZ 101 Friction Coefficient N.S.S. Hours Ferrous Corrosion N.S.S. Hours Zinc Oxidation (b) Min. Cycles APGE to Red Rust (c) Examples of Part Applications WSS-M21P44-A Silver 6 to 12 NA NA 480 hours NA 15/30 Parts for interior and exterior use especially where good c
34、orrosion protection and electrical conductivity are required, brackets, clips, stampings and tubing. WSS-M21P44-A3 Black 18 to 30 Mean: 44-49 3 Sigma: 38-55 Mean: .14 +/- .01 3 Sigma: .14 +/- .03 960 hours 480 hours 30/60 Parts for interior and exterior use where excellent corrosion protection is re
35、quired, externally threaded fasteners M4.2 and larger, brackets and stampings. (a) Based on WZ101 test program B for M10x1.5 PC 8.8 surrogate bolt. Torque values taken 25.3 kN tension. (b) It is a characteristic of ZnNi that it will produce thin and adherent layers of zinc oxide corrosion products,
36、often referred to as gray veil, as it slowly sacrifices itself. Visible and voluminous zinc oxidation is characterized as corrosion products, induced by a neutral salt spray cabinet, which are clearly visible when wet and have affected surface topography on non-post formed surfaces and fasteners in
37、accordance with SAE/USCAR-1 section 5. (c) Based upon Fasteners installed into test panels and testing in accordance with FLTM BI 123-02. Test results are for comparative purposes only and do not necessarily correlate to actual APG performance. The number left of the slant line indicates the APGE performance when tested against cathodic electrocoated cold rolled steel panels. The number right of the slant line indicates the APGE performance when tested against primed, painted and clearcoated 6111-T4 aluminum panels.
