1、 WORLDWIDE ENGINEERING STANDARDS Material Specification GMW15056 Thin Organic Precoatings Copyright 2012 General Motors Company All Rights Reserved August 2012 Originating Department: GME Specification Center Page 1 of 15 1 Scope This standard covers the requirements for thin organic precoatings app
2、lied to a hot dip coated or electro-galvanized sheet steel substrate. The substrate may be cold or hot rolled sheet steel. 1.1 Material Description. Thin organic precoatings are applied on zinc plated coil material by no-rinse technique. To realize good adhesion, chromium-free adhesion promoters are
3、 used. For improved adhesion and creep back resistance a passivation can be applied before the application of the adhesion promoter itself. The thin organic precoating can be based on different polymer systems like epoxy, polyurethane, polyacryl or polyester. The weldability is guaranteed by pigment
4、s. At present time, thin organic precoatings are not used for outer surfaces because of paint appearance aspects. First generation products are not suitable on Bake-hardening substrates because of higher curing temperatures. 1.2 Symbols. Not applicable. 1.3 Typical Applications. Thin organic precoat
5、ings serve to improve the corrosion protection of flanges and contact faces which cannot at all or only insufficiently be protected from corrosion by secondary measures such as E-coating, application of hem flange sealants or cavity waxing. 1.4 Remarks. Not applicable. 2 References Note: Only the la
6、test approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. EN 10049 ISO 20482 ISO/TS 16949 2.2 GM Standards/Specifications. 9984001 GMW3032 GMW14058 GMW14872 B 040 0180 GMW3059 GMW14058 GMW15200 EMS.ME.1508 GMW3221 GMW14085 GMW15282 GM6180M GMW3224 GMW1
7、4124 GMW15416 GME8689 GMW3286 GMW14700 GMW16549 GMW2 GMW3399 GMW14704 GMW8 GMW14019 GMW14729 GMW11 GMW14057 GMW14829 2.3 Additional References. TMC003 Material Safety Data Sheet guidance documents (available at ). Opel Method J-16 GWS-1M GWS-5A SEP 1160 (Stahl-Eisen-Prfblatt) Provided by IHSNot for
8、ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15056 Copyright 2012 General Motors Company All Rights Reserved August 2012 Page 2 of 15 3 Requirements 3.1 Requirements on Test Specimens. Reference GMW3221 Code D. 3.2 Requirements on D
9、elivery. 3.2.1 Chemical Requirements. 3.2.1.1 Base Metal. The base metal chemical composition shall conform to the requirements specified in the applicable material specification GMW2, GMW3032 or GMW3399. 3.2.1.2 Coatings. The thin organic precoating shall be tempered completely and shall not contai
10、n any volatile organic compounds. The grain size of the pigments has to be minimized by the supplier to receive a homogeneous, smooth surface quality. The pigments may not cause abrasion and wearout of dies and tools. For the zinc precoating below the thin organic precoating the requirements of GMW8
11、 or GMW11 are valid. Both coatings together may contain 75 ppm maximum Cadmium and 100 ppm maximum Lead and must meet the requirements according to GMW3059. Furthermore the coatings shall not contain trace elements which are detrimental to adhesive bondability or coatability. 3.2.1.3 Surface Treatme
12、nt. Products coated with a designated lubricant (e.g., mill oil or prelube) shall comply with GMW14019 and/or be approved by the local business unit. See the Deviations section. 3.2.2 Mechanical Requirements. 3.2.2.1 Coated Base Metal. The mechanical properties of the coated base material in as-deli
13、vered condition shall conform to the requirements specified in the applicable material specification GMW2, GMW3032 or GMW3399. 3.2.2.2 Cross Hatch Test. Flat Panels. The adhesion of the thin organic precoating shall be tested on a flat test sample, degreased with cleaning benzine, by cross hatch tes
14、t according to GMW14829 for each coated side. After stripping with adhesive tape the result shall be Rating 0. Sample size: 200 mm x 300 mm, 4 to 6 cross hatches on each side. Deep Drawn Panels. Three flat test samples 100 mm x 200 mm, degreased with cleaning benzine, shall be provided with three cr
15、oss hatches each according to GMW14829. The cutted zones shall be deep drawn according to ISO 20482 (Erichsen Cupping Test, deformation depth: 6.3 mm). The cross hatches shall be appearing in the center of the deformations, laying on the outer side. After stripping with adhesive tape, the adhesion o
16、f the coating shall be checked. Results Rating 0 to 1 are permissible. For two side coated material each side shall be tested. 3.2.2.3 Coating Adhesion Test. (Qualification testing) Coating adhesion of thin organic pre-coatings to the substrate is evaluated on degreased samples (3 minimum per test c
17、ondition) that have been adhesively bonded and subsequently investigated by lap shear testing as described in GMW15200-HS-IR-FS with a GM-approved high strength impact resistant full spectrum adhesive. The adhesive shall be cured in an air circulating oven for 25 minutes at (+175 5) C (object temper
18、ature). On one set of samples an “Initial Test” should be performed at ambivalent temperature, on the other set a “Cold Test” at -40 C, both as described per GMW15200. Exhibiting “initial” lap shear strengths 16 MPa, exhibiting “cold test” lap shear strengths 12 MPa are required for each of the test
19、ed samples. Cohesive separation within the adhesive (preferred) or delamination of thin organic precoating to the substrate that occurs above the specified minimum strength levels are considered acceptable separation modes. The bond strength and fracture mode shall be reported. 3.2.2.4 Methyl Ethyl
20、Ketone (MEK) Test. By the MEK-Wipe-Test, the adhesion of the thin organic precoating shall be tested on a flat test sheet, size: 200 mm x 300 mm, degreased with cleaning benzine. Use an 80 cm x 100 cm, 100 % cotton bleached (thread position 10/7) polishing cloth (e.g., B 040 0180), wetted with methy
21、l ethyl ketone and fixed to the base of a weight (1 kg mass). Note: The polishing cloth shall be wet during the complete test duration! The weight shall be moved on the test sample back and forth without pressure. One movement back and forth corresponds to one double stroke. The test length shall be
22、 | 25 cm. After the defined number of double strokes the appearance of the thin organic precoating shall be checked. Areas within 4 cm distance from the turning points are not be taken into account. Within the checked length the thin organic precoating shall be complete and not show loss of adhesion
23、. Slight lightening is permissible. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15056 Copyright 2012 General Motors Company All Rights Reserved August 2012 Page 3 of 15 Minimum Requirement for Products with Z
24、inc Pigments: Ten double strokes. 3.2.3 Physical Requirements. 3.2.3.1 Material Thickness and Tolerance. The detailed engineering part drawing or electronic math file will specify the material thickness and tolerance. The tolerance requirements and strength levels are listed in GMW3224. 3.2.3.2 Coat
25、ed Base Metal. The physical properties of the coated base material in as-delivered condition shall conform to the requirements specified in the applicable material specification GMW2, GMW3032 or GMW3399. 3.2.3.3 Coating Mass. The coating mass of the thin organic precoating shall be investigated by c
26、hemical stripping with concentrated sulfuric acid (water-free, 98 % minimum) and gravimetric determination. Test sample size shall be 2000 mm minimum with a preferred sample size of 2500 mm. The test sample shall be degreased with cleaning benzine, dried and weighed with 0.0001 g accuracy. Afterward
27、s one side is covered with an acid resistant adhesive tape that only the investigated sample side is in contact with the paint remover. The sample shall be dipped completely in the sulfuric acid. The dissolution time depends on the type of thin organic precoating. After removing the thin organic pre
28、coating, the sample shall be washed with deionized water until the sulfuric acid is completely removed. The adhesive tape has to be stripped off and if necessary loose sticking particles have to be removed. No residual thin organic precoating on the investigated side and adhesive tape shall be obser
29、vable. After drying, the sample shall be weighed with the same accuracy. From mass difference and sample geometry the coating mass can be calculated. If the initial testing is outside the specified coating mass range as shown in Appendix A, Table A1, three additional specimens shall be taken 25 mm m
30、inimum from the edges of the coil. The average of the three replicate specimens must conform to the specified range. Each sample must meet the minimum requirement for the coating mass. Note: Other coating masses may be used by exception. 3.2.3.4 Coating Thickness. For conversion between coating thic
31、kness and coating mass, the dry film density for the relevant thin organic precoating, according to Appendix A, Table A1, shall be used. Coating thickness measurements may be used for routine quality control evaluations. Coating thickness measurements using a suitable layer thickness gauge or from a
32、 specimen cut perpendicular to the panel surface. Suitable instruments for evaluation of coating thickness (e.g., Betascope or metallurgical microscope) shall have a capacity of 1.0 m accuracy. When using a metallurgical microscope, standard mounting practices shall be used and thickness shall be me
33、asured at 1000 x magnification. In case of disagreements between the supplier and purchaser, the weigh-strip-weigh method shall be the reference, as specified in paragraph 3.2.3.3. Note: Coating thicknesses are shown for reference only, not for conformance to specification requirements. 3.2.3.5 Corr
34、osion Resistance. For further tests see Deviation Section. 3.2.3.5.1 Cyclic Corrosion Test with Glass Flanges. (Qualification testing) For each side with thin organic precoating three replicate test samples shall be evaluated. The samples shall be prepared according to Appendix B and tested to GMW14
35、872, UB, All, 4 salt spray per cycle, method 1/2, Exposure D and GMW14124, cycle U. Requirements: 1st Generation Products: GMW14872: (34 3) cycles, (217 13) m GMW14124, cycle U: 10 cycles 2nd Generation Products: GMW14872: (68 7) cycles, (430 17) m GMW14124, cycle U: 20 cycles After the minimum test
36、 duration the samples shall not show any corrosion of the base steel. Corrosion of the pre-coatings is allowed. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15056 Copyright 2012 General Motors Company All Righ
37、ts Reserved August 2012 Page 4 of 15 3.2.3.6 Coating Surface Quality. The steel shall be free from surface defects as negotiated between purchaser and supplier. Mechanical defects of the thin organic coating such as scratches, notches or defective coating, blisters, cracks, splits, etc. are inadmiss
38、ible. Exposed (E) surfaces shall have a homogeneous surface quality without any stripes or orange peel. The grain size of the pigments shall meet the requirements for the appearance of a high quality paint coating. For unexposed (U) surfaces, slight discolors and stripe structures, which do not affe
39、ct adhesion, corrosion resistance, formability or the application of surface coatings are allowed. Certain applications require that both surfaces be of exposed (E) surface quality. 3.2.3.7 Surface Texture. Specific requirements for the texture for each region are detailed in the Deviation sheet. 3.
40、2.4 Additional Requirements. 3.2.4.1 Marking. If ink for marking is allowed by the local business unit, the ink shall not interfere with welding and paintability, shall not transfer to the opposite side or print through during part fabrication. For outer panels the marking shall be performed on the
41、unexposed surface and on the outer side of coils for inner panels. The marking shall be agreed upon between the supplier and purchaser. The ink used for marking shall be released by the purchaser. 3.2.4.2 Other Requirements. Requirements such as tolerances on product shape and dimensions, test proce
42、dures, inspection units, number of tests, sampling, test conditions, retests, inspection documents, packing and handling of disputes shall be agreed upon between supplier and the local business unit. 3.3 Processing Requirements. 3.3.1 Chemical Requirements. 3.3.1.1 Compatibility with Process Agents
43、(Qualification testing). The compatibility of thin organic precoatings with agents used in the phosphating process (cleaning, activation, phosphating, passivation and spray or immersion application) shall be tested on three test specimens 100 mm x 50 mm for each agent. The process agents which shall
44、 be used for testing have to be agreed with the responsible department. After degreasing with cleaning benzine and drying, the samples shall be weighed (0.0001 g accuracy) and dipped in the process agent for 30 minutes. The test temperature shall be the same as the relevant process temperature. The
45、test specimens shall be covered completely with the process agent. After exposure the samples shall be cleaned with de-ionized water and dried five (5) minutes at +120 C. After the samples have been cooled down to ambivalent temperature of (+23 5) C they shall be weighed with the same accuracy again
46、. Mass loss of the organic precoating 10 % by mass is permissible. The thin organic precoating shall not show any visible changes or loss of adhesion. 3.3.1.2 Compatibility with Corrosion Prevention Wax. (Qualification testing) The wax compatibility requirements of GMW15416 “High Humidity Environmen
47、ts“ shall be met for cavity and underbody wax. The test sample preparation shall be performed according to GMW15416. After the prescribed test duration the corrosion preventives shall not cause any visible changes or a quality loss of the organic coating. For evaluation the wax film shall be removed
48、 with cleaning benzine. 3.3.2 Mechanical Requirements. 3.3.2.1 Abrasion of Thin Organic Precoating. In comparison to zinc-plated surfaces (electrolytical- or hot-dip-galvanized) with identical coating masses, the organic precoated material shall not show any significant differences during processing
49、 (especially in view to tool workout, amount of precoating abrasion and tool cleaning). 3.3.3 Physical Requirements. Not applicable. 3.3.4 Additional Requirements. 3.3.4.1 Pre-Treatment / Paint Adhesion. On surfaces with thin organic precoating the formation of a closed phosphate layer is not given. Nevertheless they shall meet the overall requirements with regard to paint adhesion. After application of production representative pre-treatment an
