This study is a key reason why GMP became popular as an accelerated laboratory corrosion test for steel. In recent years GMP has been replaced by. of the reference specimens in the as-received condition are in Figure 3. The salt fog test used an abbreviated procedure (Table 3) of the standard GMP test. Find the most up-to-date version of GMP at Engineering
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The spray nozzle shall be such that the salt solution is atomized into a mist as required.
Engineering drawings and material specifications that reference this test procedure must specify the test duration, A, B, C or D or the number of test cycles as indicated in Table 1. The number of coupons required for different test durations are shown in Table 1. Test durations C and D or any modified test are to be used for validation and development purposes. The test procedure provides a combination of cyclic conditions salt solution, various temperatures, humidity, and ambient environment to accelerate metallic corrosion.
GM P Cyclic Accelerated Corrosion Analysis of Nonchromate Conversion – Google Books
In this context they can be considered to be equivalent and interchangeable terms. A cycle is made up of the daily events or test inputs prescribed in Table 4. The mist application occurs while the samples and coupons are in the ambient environment.
Originally developed by General Motors the standard has gained popularity for corrosion tests within the automotive industry and has also become the preferred corrosion test of the US Navy. A siphon spray powered by oil-free regulated air or a hand operated pump spray may also be used. The coupon mass loss values shown in Table 2 are used to verify that the correct amount of corrosion has been produced by the test.
The dryoff environment area shall be maintained with sufficient air circulation to prevent temperature stratification, and also allow thorough drying of the material.
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The procedure is effective for evaluating a variety of corrosion mechanisms, such as general, galvanic, crevice, etc. Also, synergistic effects due to temperature, mechanical and electrical cycling can be comprehended by this test.
A phase is made up of a predetermined number of cycles, 8 cycles constitute 1 phase. The quantity of spray applied should be sufficient to rinse away any salt accumulation left from previous sprays.
Please note The test standard summaries are for general guidance only. Typical test duration is 4 cycles for under dash mid to high mount locations and 12 cycles for floorpan low mount locations which approximately equals 10 yearscosmetic corrosion exposure. Test durations A and B can be used as both QC tests and validation tests depending on the 9504p of the test. Test durations A and B can be used for quality control and validation procedures as appropriate.
GMP | Standards | Ascott Analytical
However, thicker coupon sizes should be used for tests with long durations. The test sample s shall be inspected for corrosion and photographed at the end of predetermined cycles. But we haven’t supported older browsers like IE8.
In recent years GMP has been replaced by its successor; GMW, but this is all but identical in terms of the test conditions required. Method Test specimens in the enclosed chamber are exposed to a changing climate that generally comprises of the following 3 part repeating cycle variations to this cycle are permitted depending on the type of component under test — refer to the full test standard for further guidance.
The bolt, nut and washers shall be made from a non black plastic material, preferably nylon. See Appendix A for typical modifications. If the actual mass loss does not coincide with the targeted values listed in Table 2 the test should be repeated. If possible, mount test specimens in a production representative orientation simulating onvehicle inputs e. Test equipment used shall be documented and include the following information: If all solid materials are added dryan insoluble precipitate may result 3.
Typically, the time from ambient to the wet condition should be approximately 1 h and the transition time between wet and dry conditions should be approximately 3 h. One 1 test cycle is equal to 24 h, 1 phase is equal to 8 cycles. So this information should not be used as a substitute for referring to a complete test standard, at an appropriate revision level.
Website design by Peter Bourne Communications. The test duration can be individually tailored to achieve any desired level of corrosion exposure. The test consists of alternating wet and dry cycles with precisely prepared salt solution.