1、 ENGINEERING MATERIAL SPECIFICATIONDate Action Revisions 2005 02 03 Activated Para 3.0, 3.2, 3.4, 3.5, 3.7, 3.8 para 2.1, 3.0.1, 3.7.2, 3.8.1 3.8.9 title revised on 3.4 & 3.6 D. Drobnich 2004 03 17 Revised Returned to active status, rev para 1, 3.4 and 4.2 B. Curtiss 1999 12 08 Activated H. Martins,
2、 K. Yerdon Printed copies are uncontrolled Copyright 2005, Ford Global Technologies, LLC Page 1 of 4 PLATING, TIN/ZINC ALLOY, ELECTROPLATED, WSS-M1P95-A1/A4 OVER FERROUS BASE METAL 1. SCOPE These specifications define the physical and chemical properties required of a neutral electroplated tin-zinc
3、alloy and its associated hexavalent chromium free passivate in order to provide the requirements of corrosion resistance and electrical conductivity. All processes are free from hexavalent chromium, lead, and cadmium. 2. APPLICATION These specifications were released to provide corrosion protective
4、and electrically conductive coatings over steel fasteners and small parts. These coatings are also suitable for fasteners that are formed during installation (e.g. blind rivets, blind anchor nuts) and small non-electrical components. 2.1 SERVICE TEMPERATURE Due to the low melting point of tin-zinc a
5、lloy (197 C), the maximum service temperature is 190 C. These coatings are not recommended for body-in-white parts, parts that will be subsequently electrocoated, or parts subjected to high service temperatures for extended periods. 3. REQUIREMENTS 3.0 STANDARD REQUIREMENTS FOR PRODUCTION MATERIALS
6、Material suppliers and part producers must conform to the Companys Standard Requirements for Production Materials (WSS-M99P1111-A). 3.0.1 Approved Applicator Quality Requirements Applicators must follow coating manufacturer procedures and recommendations for chemical usage, equipment, analysis and p
7、rocessing. 3.2 CHEMICAL COMPOSITION BY WEIGHT TIN ZINC 65 to 85% 15 to 35% ENGINEERING MATERIAL SPECIFICATIONWSS-M1P95-A1/A4 Printed copies are uncontrolled Copyright 2005, Ford Global Technologies, LLC Page 2 of 4 3.3 PLATING THICKNESS (ASTM B 487) Plating thickness requirements represent minimum v
8、alues and apply to all significant surfaces unless otherwise specified on the engineering drawing. A1 5 Micrometers A2 8 Micrometers A3 10 Micrometers A4 13 Micrometers 3.4 CORROSION RESISTANCE (SAE/USCAR-1, FLTM BI 123-02, ARL 18-0034) After completing the specified corrosion cycles, components pla
9、ted to these specifications must meet the Corporate Standard for corrosion resistance. Thickness Designation Salt Spray Hours APG/APGE White Corrosion Red Corrosion 1% Red Rust Hours Hours Cycles A1 48 400 10 A2 48 500 20 A3 48 600 25 A4 48 700 30 3.5 CONDUCTIVITY Conductivity testing shall be run w
10、ith production representative parts and finishes assembled in a manner that represents normal assembly practice. Testing shall be conducted using the Four Terminal Gold Contact measurement method and applying normal hand applied force. The total resistance, including finish, shall be no greater than
11、 1 milliohm. Any change to this requirement or approved sources requires concurrence of the Electrical Engineering Components group. 3.6 ADHESION (ASTM B 571) Adhesion of the electro-plate to the base metal must conform to the requirements of the following test methods per ASTM B 571 3.6.1 Grind Saw
12、 Test No lifting or peeling of the substrate is permitted following grind saw test. ENGINEERING MATERIAL SPECIFICATIONWSS-M1P95-A1/A4 Printed copies are uncontrolled Copyright 2005, Ford Global Technologies, LLC Page 3 of 4 3.6.2 Burnishing Test No blistering, lifting or peeling of the electroplate
13、from the substrate is permitted following the burnishing test. 3.7 EMBRITTLEMENT (WSS-M99A3-A) Parts plated to these specifications shall be free from the detrimental effects of hydrogen embrittlement or other factors which result in part brittleness. All parts shall meet the requirements of WSS-M99
14、A3-A except as noted. 3.7.1 If hydrogen embrittlement relief via heat treatment is required, post treatments will be performed after heat treatment. 3.7.2 Due to the low melting point of tin-zinc alloy (197 C), parts requiring de-embrittlement shall be heated to a part temperature of 187 +/- 5 C and
15、 held at this temperature for a minimum of four hours. 3.8 PROCESS REQUIREMENTS In order to successfully and repeatedly process this Tin-Zinc plating the following features must be incorporated into the process line. 3.8.1 Filtered rectification, less than 5 % ripple over the full range of rectifier
16、 output. Rectifier to have Automatic Voltage Control (AVC)/Automatic Current Control (ACC). 3.8.2 Dedicated heating and cooling equipment to hold process temperature to recommended level of 18 +/- 4 C. 3.8.3 Continuous instrument monitoring of temperature and pH for all process stages, with recorder
17、s. 3.8.4 Continuous plating bath recirculation. 3.8.5 Continuous plating bath filtration with 2 to 3 turnovers per hour. 3.8.6 Testing devices for plating thickness and alloy such as X-ray or Atomic Absorption. 3.8.7 Analytical equipment for titration and hull cell testing. 3.8.8 Certification of ti
18、n/zinc anodes is required for less than 1/2 of 1 percent of metal impurities. 3.8.9 Conventional Neutral Bath, pH of 6 to 7. 3.9 THREAD ACCEPTANCE REQUIREMENTS (WA900, WE900, WX100) For thread acceptance requirements see Ford Worldwide Fastener Standards WA900, WE900, and WX100. ENGINEERING MATERIAL
19、 SPECIFICATIONWSS-M1P95-A1/A4 Printed copies are uncontrolled Copyright 2005, Ford Global Technologies, LLC Page 4 of 4 3.10 CLEANING Prior to plating, the substrate shall be free of oil, dirt, and similar foreign materials. If a cleaning process is necessary, it shall have no detrimental effect on
20、the substrate, including freedom from embrittlement. 4. GENERAL INFORMATION The information given below is provided for clarification and assistance in meeting the requirements of these specifications. 4.1 SIGNIFICANT SURFACES Unless otherwise specified on the Engineering Drawing, significant surfac
21、es are defined as those surfaces of the finished part that: Are directly visible and/or visible by reflection when the finished part is assembled in position. Can be the source of corrosion products directly visible or visible by reflection. 4.2 TIN ZINC HEXAVALENT CHROMIUM FREE COATING AND BLACK FINISH Special finishes may be required on some parts, in which case the Engineering Drawing will be marked accordingly, for example: Tin/Zinc plate plus hexavalent chromium free passivate plus black finish.
