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 In recent years GMP has been replaced by.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 number of coupons required for different test durations are shown in Table 1. If possible, mount test specimens in a production representative orientation simulating onvehicle inputs e. If the actual mass loss does not coincide with the targeted values listed in Table 2 the test should be repeated. The test sample s shall be inspected for corrosion and photographed at the end of predetermined cycles.
Website design tm Peter Bourne Communications. This method also includes measurement of corrosion creepback from a scribe line, and describes how to evaluate corrosion formation in unscribed areas. The latest revisions include: This method does not propose to address all the safety problems associated with its use. Also, the reasons why the targeted value s was not obtained should be investigated and corrected before resuming the test.
Test Conditions The test consists of alternating wet and dry cycles with precisely prepared salt solution.
Also, synergistic effects due to temperature, mechanical and electrical cycling can be comprehended by this test. The coupon mass loss values shown in Table 2 are used to verify that the 95440p amount of corrosion has been produced by the test. The test procedure provides a combination of cyclic conditions salt solution, various temperatures, humidity, and ambient environment to accelerate metallic corrosion.
Test durations A and B can be used as both QC tests and validation tests depending on the purpose of the test. One 1 test cycle is equal to 24 h, 1 phase is equal to 8 cycles.
The test can be started at any time with the understanding that 24 h constitutes 1 cycle. In addition to the sample data and test results, reports must indicate the total number of cycles run, any modifications to the test see Appendix Athe Equipment and Test Record Form Appendix B and should include photographic documentation and the coupon mass loss values.
The ambient shift can be modified to include additional test inputs such as dust, grit sprays, mechanical cycling, electrical cycling, thermal inputs, grayelometer and acid rain spray.
The quantity of spray applied should be sufficient to rinse away any salt accumulation left from previous sprays. Coupon mass loss targets for every phase are not included in Table 2. Any option changes not called out specifically in this Appendix must be included on the engineering drawing. Longer test durations C and D and tests involving modifications are to be used for validation purposes only.
You need to upgrade your browser You are using Internet Explorer 8 This is considered an out of date browser. Refer to Table 2 for targeted mass loss values, in milligrams, for various test durations as a function of the coupon’s original thickness. Water fog or visible water droplets on parts – continuous after equilibrium is reached. Corrosion coupons shall be removed and analyzed after each phase throughout the test to monitor the corrosion.
Ambient Soak 8 h. But we haven’t supported older browsers like IE8.
GM P Cyclic Accelerated Corrosion Analysis of Nonchromate Conversion – Google Books
Both are excellent browsers. To check test progress and assure that the test is being run correctly, assume a linear corrosion rate. So this information should not be used as a substitute for referring to a complete test standard, at an appropriate revision level. This is considered an out of date browser. Humidity ramp times between the ambient and wet condition and between the wet and dry conditions are critical to test acceleration this is because corrosion rates are highest during this transition period.
To analyze coupons remove 1 coupon from each end of the rack and prepare for weighing and mass loss determination. The test is generally made up of 3 shifts: These procedure modifications are based on field knowledge combined with engineering judgment to enhance the test’s ability to predict field performance. The temperature and humidity conditions are shown in Table 3. A cycle is made up of the daily events or test inputs prescribed in Table 4.
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This procedure supersedes any old procedures that may have referenced an “A” or “B” Test Method Method A is eliminated. Test acceleration can be optimized and tracked by using standard corrosion coupons as monitoring devices. The solution shall be sprayed as a mist for example, from a plastic bottle onto the test samples and coupons. The test consists of alternating wet and dry cycles with precisely prepared salt solution.
GMP | Standards | Ascott Analytical
This process can be aided by using a commercial grade degreaser prior to methanol or acetone clean. Repeat the cycle daily as necessary until the test duration requirements are met. Use Option IV – for door detents without weatherseal protection Use Option VI – for door detents with weatherseal protection 1 test cycle is equal to 24 h, 1 phase is equal to 8 cycles.
The coupons serve to monitor the average general bare steel corrosion produced by the test environment. The number of cycle repeats and therefore the test duration is variable.
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. This method may involve hazardous materials, operations and equipment.