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1、 WORLDWIDE ENGINEERING STANDARDS Material Specification Finish GMW14083 Corrosion Protective Coating for Spring Hose Clamps Copyright 2006 General Motors Corporation All Rights Reserved August 2006 Originating Department: North American Engineering Standards Page 1 of 3 1 Scope This specification co
2、vers the basic requirements for a corrosion protective coating system for spring hose clamps per GM6298M. This coating is resistant to strong oxidizing corrosives and provides excellent adhesion properties for glued on clamp applications. 1.1 Material Description. The coating system is free of hexav
3、alent chromate and is in compliance with GMW3059 requirements. The coating system does not induce hydrogen embrittlement. 1.2 Typical Applications. The coating is suitable for constant tension clamps. The maximum continuous service temperature is 200C. 1.3 Remarks. Use of this coating system on thre
4、aded surface and/or bearing surface of joints could effect the torque-tension relationship. It is recommended that a torque-tension study of the fastener joint be performed before releasing this finish on any new application. 2 References Note: Only the latest approved standards are applicable unles
5、s otherwise specified. 2.1 External Standards/Specifications. ASTM B117 ISO 9227 ASTM D610 2.2 GM Standards/Specifications. 9985010 GM4465P 9985670 GM6277M 9985912 GM6298M 9986086 GM9071P 9986121 GMW3001 9986153 GMW3059 9986231 2.3 Additional References. US Pharmacopeia. 3 Requirements 3.1 Coating A
6、pplication. Prior to coating, the parts shall be free of oil, scale, and similar foreign materials. The mechanical cleaning process, such as shot blasting or dry honing, shall have no detrimental effect on the substrate, including hydrogen embrittlement or reduction in hardness. The coating shall be
7、 applied by the dip/spin process. The cure temperature of the coating shall not affect the mechanical properties of the clamps. 3.2 Appearance. The coating shall have uniform silver gray appearance and shall be free from tears, sags, and excessive coating that would affect performance. It shall not
8、be oily or tacky to the touch. Black color is also available. If no color is specified on the drawing the supplier will provide the coating in gray color. 3.3 Thickness. The coating thickness shall not inhibit the performance of this specification or the installation or function of the hose clamp. T
9、ypical coating thickness shall be 10 to 50 m. 3.4 Corrosion and Stress Corrosion Cracking Resistance. Hose clamp samples shall be prepared per paragraphs 3.4.1 and 3.4.2 before testing in Sodium Hypochlorite (3.5) and Cyclic Corrosion test (3.6). 3.4.1 Shipping Damage Pretreatment. All clamps used i
10、n the Corrosion and Stress Corrosion Cracking (SCC) test shall undergo the following procedure to simulate excessive handling and transportation damage. 3.4.1.1 Fill a cardboard box full of clamps to be tested. The box shall be no larger than 250 X 250 X 250 mm. 3.4.1.2 Secure the box thoroughly to
11、prevent it from breaking open. 3.4.1.3 Slowly slide the box off a surface 0.75 m above the floor. 3.4.1.4 Repeat step 3.4.1.3 30 times, alternating between top, side and bottom of box. 3.4.2 Fixturing on Mandrel. All clamps used in the Corrosion and Stress Corrosion Cracking (SCC) test shall be asse
12、mbled on a plastic mandrel with a diameter 0.2 to 0.3 mm smaller than the full open clamp diameter. The mandrel shall be 110 to GMW14083 GM WORLDWIDE ENGINEERING STANDARDS Copyright 2006 General Motors Corporation All Rights Reserved Page 2 of 3 August 2006 120 mm long and have 5 clamps per mandrel.
13、 Multiple mandrel assemblies may be used depending on sample size. 3.5 Resistance to Stress Corrosion Cracking in 5% Sodium Hypochlorite (Bleach). There shall be no evidence of cracks or fracturing of clamps after 28 h immersion in 5% Sodium Hypochlorite solution as described in the following paragr
14、aphs. 3.5.1 Each clamp and mandrel assembly shall be immersed in 2000 50 ml of 4.9 to 5.1% sodium hypochlorite solution at 23 3C in a vented plastic container. 3.5.2 The 5.0% Sodium Hypochlorite (NaOCl) SCC Test Solution shall be assayed within 72 h prior to test per the following procedure adapted
15、from US Pharmacopeia. 3.5.2.1 Weigh accurately, in glass flask, 2.2 g of Sodium Hypochlorite SCC Test Solution, and dilute with 50 ml water. 3.5.2.2 Add 2.5 g potassium iodide and 10 ml 6 N acetic acid. Titrate the liberated iodine with 0.100 N sodium thiosulfate, adding 3 ml of starch TS as the end
16、point is approached. Note: The solution is dark with a clear endpoint, so a white background is required for an accurate end point determination. 3.5.2.3 Perform a blank determination, and make any necessary correction. Each ml of 0.100 N sodium thiosulfate is equivalent to 0.003722 g of NaOCl. 3.5.
17、2.4 Calculation. % NaOCl = (A x 0.003722B) x 100/C Where: A = ml 0.100 N sodium thiosulfate B = g/ml sodium thiosulfate C = g bleach test solution 3.5.3 Examine for cracks while holding the clamp in full open position with pliers after 28 h. 3.5.4 This test is required for the initial source approva
18、ls and PPAP submission of clamps. Periodically supplier will run the test as the statistical process control test and maintain the test record in file to produce when required by GM. 3.6 Resistance to Cyclic Corrosion and Stress Corrosion Cracking. The preprepared clamps (see 3.4) shall be exposed t
19、o GM9540P. After 16 cycles exposure the clamps shall be free of red corrosion rated 8 or better per ASTM D610, and after 40 cycles exposure there shall be no evidence of cracks or broken clamps. 3.6.1 Significant surfaces for evaluation of clamps shall be all exposed surfaces of the clamp when insta
20、lled on the mandrel. Corrosion due to touch marks on the clamp ears shall be excluded from the evaluation. 3.6.2 This test is required for initial approval of chemicals/process and applicators. Supplier shall periodically run this test for the process control and maintain the test record in file to
21、produce to GM when required. 3.7 Resistance to Underhood Fluids. Coated clamps in as received condition shall be tested against the following chemicals as per the described tests. This test is required for the initial approval of chemicals/ process. 3.7.1 Deionized Water Resistance. The coating shal
22、l not blister or show any signs of red rust when subjected to immersion in DI water for 240 h at 23 2C. 3.7.2 Gasoline Resistance. The coating shall not blister or show any signs of softening or dulling when subjected to immersion in current factory fill gasoline (9986086) for 24 h at 23 2C. 3.7.3 H
23、ot Oil Resistance. The coating shall not blister or show any signs of softening or dulling when subjected to immersion in engine oil (9986231, SAE 10W30 or equivalent) for 24 h at 66 3C. 3.7.4 Engine Coolant Resistance. The coating shall not blister or show any signs of softening or dulling when sub
24、jected to immersion in a 50% solution of water and Dex Cool long life coolant concentrates (GM6277M) for 24 h at 23 2C. 3.7.5 Brake Fluid Resistance. The coating shall not blister or show any signs of softening or dulling when subjected to immersion in currently approved brake fluid (9986121) for 24
25、 h at 23 2C. 3.7.6 Power Steering Fluid Resistance. The coating shall not blister or show any signs of softening or dulling when subjected to immersion in current factory fill power steering fluid (9985010) for 24 h at 66 3C. 3.7.7 Transmission Fluid Resistance. The coating shall not blister or show
26、 any signs of softening or dulling when subjected to immersion in current factory fill transmission fluids (9985912/ 9986153) for 24 h at 66 3C. 3.7.8 Windshield Washer Fluid Resistance. The coating shall not blister or show any signs of softening or dulling when subjected to immersion in factory fi
27、ll wind shield washer fluid (9985670) for 24 h at 23 2C. 3.8 Flexibility and Chip Resistance. The coating shall withstand the normal extension and compression of spring hose clamps during assembly in the end product without evidence of GM WORLDWIDE ENGINEERING STANDARDS GMW14083 Copyright 2006 Gener
28、al Motors Corporation All Rights Reserved August 2006 Page 3 of 3 flaking or loss of adhesion to base metal. Also, it shall withstand normal handling and storage conditions without chipping, flaking or other coating damage that affects performance. 3.9 Adhesion Characteristics. 3.9.1 Humidity, Scrib
29、e, Tape Test. Parts coated to this specification shall show no evidence of blistering or other appearance changes after exposure to humidity testing per GM4465P for 96 h, minimum. When tape tested per GM9071P, Method B, 10 minutes after removal from humidity, there shall be minimum 99.0% of coating
30、retention. 3.9.2 Pull-off Test for Glued Clamps. Hose clamps may be used in Pre-Opened, Pre- Positioned (POPP) applications where the hose clamp is full opened and glued to the hose. 3.9.2.1 Glue Joint Preparation. 3.9.2.1.1 The hose shall be buffed to remove any surface texture and soil, and the re
31、sulting surface shall approximate a smooth right circular cylinder. 3.9.2.1.2 The buffed area shall be cleaned with mild soapy water, rinsed in tap water, and sprayed with isopropyl alcohol containing about 0.1% ammonia. Allow hoses to dry. 3.9.2.1.3 A 0.04 0.01 g bead of Loctite Prism 447 glue shal
32、l be laid axially in the buffed area the length of the clamp width. Note: The glue used shall be compatible to the coating, not to cause corrosion. 3.9.2.1.4 The bottom of the clamp shall be placed against the glue bead and held against it with no more than 5 N force for 30 to 60 s. The glue is then
33、 allowed to cure for 8 to 16 h. The finished glue patch shall be approximately the clamp width. 3.9.2.2 Pull-off Test. The end of the hose is fixed to one side of a tensile test stand; a hook attached to the other side of the tensile test stand is placed under the clamp body near the single tang. Th
34、e load is applied such that the clamp is pulled along the axis of the hose. Stop the test when the force exceeds 335 N and evaluate the coating at the glue joint. 3.9.2.3 Acceptance Criteria. The adhesion of the coating shall be sufficient to withstand the applied 335 N force. There shall be no sepa
35、ration of the coating from the substrate or between coating layers. 3.9.3 Elevated Temperature, Tape Test. Parts heated to 120C for 60 minutes shall not exhibit blistering, peeling, flaking or coating loss when tape adhesion tested per GM9071P. 3.10 Corrosion Resistance Test. Clamps in the as coated
36、 condition tested in Neutral Salt Spray Corrosion (ASTM B117/ISO 9227) shall meet 120 h of no white corrosion and 480 h of no red rust. This test shall be used for initial approval of chemicals. 4 Manufacturing Process Not applicable. 5 Rules and Regulations 5.1 All materials supplied to this specif
37、ication must comply with the requirements of GMW3001, Rules and Regulations for Material Specifications. 5.2 All materials supplied to this specification must comply with the requirements of GMW3059, Restricted and Reportable Substances for Parts. 6 Approved Sources Engineering qualifications of an
38、approved source is required for this specification. Only sources listed in the GM Materials File (i.e., MATSPC) under this specification number have been qualified by engineering as meeting the requirements of this specification. 7 Notes 7.1 Glossary. Not applicable. 7.2 Acronyms, Abbreviations, and
39、 Symbols. DI Deionized POPP Pre-Opened, Pre-Positioned PPAP Production Part Approval Process SCC Stress Corrosion Cracking TS Test Solution 8 Coding System This material specification shall be referenced in other documents, drawings, VTS, CTS, etc. as follows: GMW14083, or GMW14083 Black 9 Release and Revisions 9.1 Release. This standard originated in January 2005. It was first approved by Global Finish Committee in May 2006. It was first published in August 2006.