This is a cyclic corrosion test (refer to Figure A1) used for validation testing (cosmetic and/or functional/general durability), development testing, and quality control testing, for all global environmental regions.
This procedure describes an accelerated laboratory corrosion test method to evaluate assemblies and components. The test procedure provides a combination of cyclic conditions (salt solution various temperatures, humidity, and ambient environment) to accelerate metallic corrosion.
The procedure is effective for evaluating a variety of corrosion mechanisms, such as general, galvanic, crevice, etc. The test exposure/conditions can be individually tailored to achieve any desired level of corrosion exposure Also, synergistic effects due to temperature, mechanical and electrical cycling, along with other stresses, car e comprehended by this test.
The test method is comprised of 1% (approximate) complex salt mist applications coupled with high temperature and high humidity and high temperature dry off. One (1) test cycle is equal to 24 h A cycle is made up of the daily events or test inputs illustrated in Figure A1. A cycle normally requires one (1) day to complete. The test exposure is dictated by a targeted coupon mass loss.
A target range for the number of cycles necessary to meet the required mass loss is provided in Table A1 for Method 1/2 and Table A2 for Method 3. The coupon mass loss values are used to verify that the correct amount of corrosion has been produced by the test.
In addition to meeting mass loss requirements, the test must be conducted such that the number of cycles required to meet coupon mass loss requirements falls within the specified range.
Equipment
Ambient Stage:
The apparatus for the ambient stage shall have the ability to maintain the following environmental conditions:
Temperature: 25℃±3℃
Humidity: 45%±10% Relative Humidity(RH)
Duration: Approximately 8 h per cycle
Humid Stage:
The apparatus for the humid stage shall have the ability to ramp to (within 1h) and maintain (for approximately 7h) nuder the following the conditions:
Temperature: 49℃±2℃
Humidity: Approximately 100% Relative Humidity(RH)
Duration: Approximately 8 h per cycle
Water Fog:
The apparatus shall include provisions for a supply of suitably conditioned compressed air and one or more nozzles for fog generation. The nozzle or nozzles used for the generation of the fog shall be directed or baffled to minimize any direct impingement on the test samples.
At least two (2) clean for collectors shall be placed within the exposure zone so that no drops of solution from the test specimens or any other runoff source shall be collected. The collectors shall be placed in the proximity of the test specimens, one nearest to any nozzle and the other farthest from all nozzles.
Collection rates for each 80 cm of horizontal collection area should be in the range of 0.75 mL/h to 1.5 mL/h (on average) for water that is collected in the collectors within the Humid Stage. Fog collection rates may be adjusted within this range as necessary to meet mass loss target rates.
Suitable collecting devices include glass or plastic funnels with the stems inserted through stoppers into graduated cylinders. Funnels with a diameter of 10 cm have an area of about 80 cm2.
Where samples cannot be read immediately upon completion of the humid stage, closed cell foam balls can be used in combination with the collections funnels (i.e., foam ball in mouth of funnel) to allow moisture to collect while minimizing on.
Wet-Bottom:
The apparatus shall consist of the chamber design as defined in ISO 6270-2. During wet-bottom generated humidity cycles, the tester must ensure that visible water droplets are found on the samples to verify proper wetness.
Steam Generated Humidity:
Steam generated humidity may be used provided the source of water used in generating the steam is free of corrosion inhibitors. During steam generated humidity cycles, the tester must ensure that visible water droplets are found on the samples to verify proper wetness.
Steam generated humidity:
Steam generated humidity may be used provided the source of water used in generating the steam is free of corrosion inhibitors. During steam generated humidity cycles, the test must ensure that visible water droplets are found on the samples to verify proper wetness.
Dry Off Stage:
The apparatus foe the dry off stage shall have the ability to (within 3 h) and maintain (for approximately 5 h) under the following environmental conditions:
Temperature: 60℃±2℃
Humidity: ≤30% Relative Humidity(RH)
Duration: Approximately 8 h per cycle
The apparatus shall also have sufficient air circulation to prevent temperature stratification, and also allow through drying of the test samples.
Salt Mist Application:
The solution shall be sprayed as an atomized mist, and should be sufficient to raise away any salt accumulation left from previous sprays. The test samples and coupons shall be thoroughly wet/dripping. Suitable application techniques include using a plastic bottle, or a siphon spray powered by oil-free regulated air to spray the test samples and coupons.
Corrosion Coupons and Mounting Hardware:
Coupons serve to monitor the average general bare steel corrosion produced by the test environment. Coupons consist of 25.4 wide x 50.8 long x 3.18 mm thick pieces of bare SAE 1008-1010 carbon steel, cold-rolled steel per SAE J2329 CR1E. uncoated, no post-coating treatment, which are stamped with an alphanumeric identification number (reference Figure A2).
The coupons shall be secured to an aluminum or nonmetallic coupon rack with fasteners as shown in Figure A3 and Figure A4. The bolt, nut, and washers shall be made from a non-black plastic material.preferably nylon. Figure A4 shows a completed coupon rack configuration. The number of coupons recommend for different test duration are shown in Table A3.
Test Vehicle/Test Piece:
The test sample (design, surface, and preparation) should be agreed to by the parties concerned (Design Engineer/Materials Engineer/Corrosion Engineer) and should simulate actual production materials and conditions when possible.
The number of test samples selected should be sufficient to ensure that the test results are statistically significant at some predetermined confidence level. unless otherwise specified. Any unusual observations made during sample preparation should be recorded and reported as part of the test results.
Where appropriate. test samples and/or control panels of known performance, should be tested concurrently.These controls can allow the normalization of test conditions during repeated running of the test (supplementing the required mass loss controls) and may also allow comparison of test results from different repeats of the test.
Where actual/representative production samples are available and the in-service orientation is known, test samples should be oriented to simulate these conditions.
When using test panels and/or the in-service orientation is not known, the sample shall, in principle, be oriented such that it is facing upward and at an angle 20 degree ± 5dregree from vertical.
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