1、 WORLDWIDE ENGINEERING STANDARDS Material Specification GMW15854 High Temperature, Corrosion Resistant Coating for Fasteners and Small Parts Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 1 of 7 1 Scope This standard covers the requirements for a high temperature, corrosion
2、 resistant coating with friction control. This coating is for ferrous parts only. 1.1 Material Description. This coating is a dip-spin or spray type coating which provides corrosion protection in operating range from -50 C to 450 C. The coating is a baked on base coat providing corrosion protection.
3、 A lubricant-integrated topcoat or additional lubricant maintains consistent friction and is an integral part of an approved coating systems. 1.2 Symbols. Not applicable. 1.3 Typical Applications. This coating is suitable for externally threaded parts (size M6 or greater) and non-threaded ferrous pa
4、rts where high levels of corrosion protection at high temperature are required. The dip-spin process is not recommended for the following: Bolts smaller than M6 Parts with recessed features (such as internal drive screws) Loose washers of all sizes Internally threaded parts (nuts) 1.4 Remarks. 1.4.1
5、 Dip-spin Coating is a Bulk Process. If parts are prone to nesting, stick together (flat washers), or easily damaged by mechanical tumbling, do not use dip-spin coating method. Alternatives include spray and dip-drain methods. 1.4.2. Use of this coating system on threaded surface and/or bearing surf
6、ace of joints could affect 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. 1.4.3 Polytetrafluoroethylene (PTFE) shall not be used in topcoat or lubricant for this specification due
7、to the expected high operating temperatures. 1.4.4 This coating process does not generate hydrogen; however, pre-treatment processes, i.e., acid pickling, could cause hydrogen adsorption. See precautions in 3.1.1. 1.4.5 The corrosion performance is influenced by part geometry, substrate material, an
8、d application process. The coating systems approved to this specification were tested to meet all requirements using common steel parts. For new designs, applications, and parts with complex geometries, or difficult to clean material such as castings and powder metal, extra validation testing is hig
9、hly recommended. 1.4.6 Special design and process consideration must be made when applying this coating on surfaces that are part of a clamped joint. This includes the bearing surface against which the bolt underhead comes in contact. On a bolt, stud, or screw, this includes the underhead bearing su
10、rface. Excessive coating may creep resulting in loss of clamp load. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. AIAG CQI-12 ISO 16047 ISO 1463 ISO 17025 ISO 4014 SAE/USCAR-5 ISO 9227 2.2 GM Standards/Specific
11、ations. 9985670 GMW14700 9985809 GMW14729 9986153 GMW14829 9986333 GMW14872 GMW3059 2.3 Additional References. GM Part No. 11570102 GM Part No. 11611954 GM Part No. 11612005 or 11611987 TMC003 Material Safety Data Sheet guidance documents (available at ). Copyright General Motors Company Provided by
12、 IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15854 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 2 of 7 3 Requirements 3.1 Pre-treatment and Post-treat
13、ment. 3.1.1 The use of acidic cleaners is not recommended as a pre-treatment for parts heat treated or highly cold worked to the specified core or surface hardness of HRc 35 or higher. If acidic cleaning is performed in pre-treatment, process parts per SAE/USCAR-5. 3.1.2 The temperature of the curin
14、g process shall be 400 C maximum. This is to reduce the risk of tempering or other softening conditions to heat treated parts. For heat treated parts, special consideration shall be made to ensure the mechanical properties are not detrimentally affected by the coating process. 3.2 Appearance. The co
15、ating shall have a uniform appearance and shall be free from tears, open pores, cracks, flakes, blisters and uncoated areas. The coating shall not be oily or tacky to the touch. During normal handling, practice parts shall not leave particulate residue on equipment, hands, or gloves. Unless otherwis
16、e specified, the color shall be silver or gray. 3.3 Coating Thickness. 3.3.1 The minimum coating thickness shall be 15 m except on the threads of fasteners. 3.3.2 When applied to threaded fasteners, the coating shall not have adverse effects on normal installation and removal. Coating thickness shal
17、l be adequate to meet corrosion resistance performance requirements. The maximum coating thickness on threaded products is limited by the basic thread size (tolerance h or H). After coating, parts must gage with appropriate basic size GO thread gages. Threads may be produced undersize/oversize (befo
18、re coating) to accommodate the coating thickness, provided the finished product (after coating) meets all specified mechanical properties. Where mechanical properties are not specified, undersizing/oversizing is subject to approval by the pertinent engineer and all undersize/oversize shall be within
19、 permissible limits as agreed upon. The fastener supplier will consult with the coating applicator to determine the appropriate thread size before coating. 3.3.3 For non-threaded parts, maximum coating thickness is not defined. However, the coating thickness shall not have adverse effects on the fit
20、, form, and function of the component. 3.3.4 For referee purposes, the coating thickness shall be determined by microscopic examination of cross sections taken perpendicular to significant surfaces per ISO 1463. In this test, cracks, open pores, and other discontinuities in the coating exposing the
21、substrate is not allowed unless it is less than 100 m in size and spaced more than 100 m apart. 3.4 Corrosion Resistance. 3.4.1 Coated parts shall show no base metal corrosion (red rust) after 720 h of neutral salt spray (NSS) per ISO 9227. Parts undergoing this test must not go through extended hea
22、ting processes outside of the regular curing process except when testing per 3.6. Note: The salt spray test is only used to test the integrity of the finish for quality control. The hours to red rust shall not be construed as having any correlation to the actual service life of the part. 3.4.2 Signi
23、ficant surfaces for test evaluation of fasteners shall be all exposed surfaces of the fastener when installed including, but not limited to, fastener heads, socket recess, SEMS (screw-washer assembly) washers and external surface of nuts. Fastener threads and point are excluded unless otherwise spec
24、ified on the drawing. 3.4.3 Significant surfaces on parts other than threaded fasteners shall be all surfaces. Deep recesses, such as blind holes and the interior of tubes are excluded unless otherwise specified on the drawing. 3.5 Cyclic Corrosion. Parts coated to this specification shall be expose
25、d to cyclic corrosion test per GMW14872, UB, All, 4s, Method 1/2, Exposure D with a thermal soak addition (Option 4) for 4 h at 350 C. After exposure, there shall be no red rust on significant surfaces. 3.6 High Temperature Corrosion Resistance. After heating the parts for 4 h continuously at 450 C
26、(part temperature), the corrosion resistance requirements as specified in 3.4 and 3.5 shall be met. 3.7 Flexibility and Chip Resistance. The coating must withstand the normal extension, flexing and compression encountered by springs and spring clips during product assembly without evidence of flakin
27、g or loss of adhesion from the base metal. It shall withstand normal handling and storage conditions without chipping or flaking. 3.7.1 Test coated part per GMW14700, Method C. A minimum rating of 7 is required. 3.8 Adhesion Characteristics. 3.8.1 Parts coated to this specification shall show no evi
28、dence of blistering or other appearance changes, other than a whitish blush, after exposure to humidity testing per GMW14729 for 96 h minimum. When tape tested per GMW14829, Method B, 10 minutes after removal from humidity Copyright General Motors Company Provided by IHS under license with General M
29、otors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15854 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 3 of 7 test there shall be minimum 99.0% of coating retention after the tape adhesion t
30、est. When removing the tape, a slight adherence of the coating is permissible since this has no influence on the corrosion resistance. In case of small fasteners when the surface area of the part is not large enough to run the test, steel panels 50 x 50 mm shall be processed with fasteners and used
31、for adhesion test. 3.8.2 For regular production, each coating lot shall be tested per 3.8.1, except omit the humidity exposure. If a particular part is too small for this test, a surrogate steel panel may be coated along with the same lot and used for testing. 3.9 Chemical Resistance. Coated parts s
32、hall be immersed in the following underhood fluids for 24 h at 23 C 2 C. After exposure, the coating shall not blister or show any signs of softening or dulling. Engine oil (SAE 5W30 or equivalent) 50% mixture of potable water and extended life coolant (9985809) DOT 4 brake fluid Transmission fluid
33、(9986333 or 9986153) Windshield washer fluid (9985670) 3.10 Friction Control. Coatings to this specification shall include lubrication for friction control. See Appendix A, Testing Requirements. 3.10.1 Coefficient of Friction Test. The coefficient of friction of threaded fasteners shall be 0.13 0.03
34、 when tested per ISO 16047 with the following additional requirements: For studs and bolts with non-rotating heads, or short bolts (effective length from head to first full thread 3d), a surrogate bolt (GM Part No. 11570102) can be used for friction testing. The surrogate bolt must be coated togethe
35、r with the production parts under the same process. Test washer shall be according to ISO 16047, type HL, except with surface roughness of 0.2 to 0.8 Ra and plain (uncoated) surface (reference GM Part No. 11611954). Stamped identification is not allowed on the washer surface. Test washers must be ul
36、trasonically cleaned and degreased within 2 h prior to test. Test nuts shall be according to ISO 16047 with plain surface, uncoated and degreased (GM Part No. 11612005 or 11611987). Test nuts must be ultrasonically cleaned and degreased within 2 h prior to test. Test bolt shall be according to ISO 1
37、6047 with plain (uncoated) surface. Bolts must be ultrasonically cleaned and degreased within 2 h prior to test. For testing of all fasteners, the length of the protrusion of the bolt shall be two to seven thread pitches when the nut is seated against the test washer or test device. There shall be a
38、 minimum of two full threads within the clamp length after tightening. When testing bolt/screw-washer and nut-washer assemblies, the production part washer shall not be fixed against rotation. Do must be based on the bolt head bearing surface outer diameter Dw min. Tightening speed shall be 30 rpm 3
39、 rpm. Do not wash or precondition the coated fastener to be tested. (This may change the frictional property of the coating and affect the test result.) 3.10.2 Requirements for Chemical Approval. Process test bolts using production equipment with regular production-loading weights and other environm
40、ents. This includes pre-treatment, coating, post-treatments, and transportation. The coefficient of friction test shall be performed by an ISO 17025 accredited laboratory. Apply coating to M10 x 1.5 mm x 60 mm property class 10.9 hex head bolt per ISO 4014, Grade A. Thread tolerance shall be 6 h aft
41、er coating. Perform test according to 3.10.1 except use the test washers GM Part No. 11611954 (steel with plain finish). The bolt is the driven part. For each washer type, the coefficient of friction 3 sigma values based on 30 samples are required to be within the specification. See Appendix B, Chem
42、ical and Application Approval. 3.10.3. Requirements for Applicator Approval. The applicator shall perform test per 3.10.1 with only test washer GM Part No. 11611954 (steel washer with plain finish). The test bolt must be processed through the applicator using the same equipment and process handling
43、as regular production. The coefficient of friction test shall be performed by the applicator. 3.10.4 Requirement for Production Part Approval Process (PPAP). Test production fastener according to 3.10.1, friction values for 30 samples shall be within the specification. 4 Manufacturing Process The GM
44、-approved process, including pre-treatment (cleaning), coating, and post-treatment shall be performed by one company in one facility. The equipment, process controls, chemicals, and location used must remain the same for regular production. This includes pre-treatment (such as Copyright General Moto
45、rs Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15854 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 4 of 7 cleaning) and post-treatm
46、ent. These operations cannot deviate without prior approval by GM. For each production lot of coated parts, the applicator shall supply a certificate to their customer with the following information: This specification number Applicator name and address Coating system used Part number Date(s) the pa
47、rts were coated Coating thickness Coefficient of friction test results at PPAP Coefficient of friction test results as per most recent process control test Note: Coefficient of friction test not applicable for non-threaded fasteners. The applicator shall keep the certificates for a minimum of 5 year
48、s. 5 Rules and Regulations 5.1 Legal Regulations. All materials must satisfy applicable laws, rules, regulations and recommendations valid in the country of usage. 5.2 Language. In the event of conflict between the English and domestic language, the English language shall take precedence. 5.3 Inspec
49、tion and Rejection. Samples of components or materials released to a GM material specification shall be tested for conformity with the requirements of this material specification and approved by the responsible Engineering department prior to commencement of delivery of bulk supplies. A new approval must be received for any changes, e.g., properties, manufacturing process, location of manufacture, etc.
