The GMW 15891 standard, developed by the General Motors company, which includes brands such as Buick, Cadillac and Chevrolet, describes a test method to determine the hardening of a coating on painted metal or plastic parts and test panels.
This test method describes a solvent scrubbing technique for evaluating the solvent resistance of an organic coating that changes chemically during the curing process. This technique can be used in the laboratory or in the field.
Every paint technology requires a solvent suitable for that technology. A suitable solvent should be used as agreed between the paint supplier and the responsible General Motors engineer.
During testing, samples are cut from the parts being evaluated, to the extent that the size and geometry of the part permit. If this is not possible, custom test plates representing the production section are prepared using the same substrate material, substrate thickness, surface preparation (such as phosphating or anodizing), and coating material. If this test is performed for quality control purposes, the test procedure is carried out on finished parts or vehicle bodies. For technology approvals, painted samples must be allowed to age according to the relevant material specification before this curing test is performed.
During the test, the fabric is folded into quarters and saturated with the appropriate solvent. Excess solvent is squeezed out and testing begins immediately. Hard pressure is applied while rubbing. Ten pairs of rubs are applied to the sample, with a 25 mm to 50 mm reciprocating motion. The contact area must be at least 16 mm in diameter.
When interpreting the results, test samples are evaluated by examining the paint residue on the painted surface and the scouring pad. Samples are graded according to the grading scales immediately after the test is completed. If the sample to be tested is an electrodeposition coating, primer surface, conductive primer, or monocoat, Table 1 in the standard is used; if the sample has a transparent coating, Table 2 is used.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides solvent friction test services to determine the cure of painted metal or plastic surfaces, within the scope of the GMW 15891 standard, with its trained and expert staff and advanced technological equipment.
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