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GMW14872 Cyclic Corrosion Laboratory Test

The GMW14872 cyclic corrosion laboratory test is a crucial quality assessment technique used by industries to evaluate the durability and corrosion resistance of materials and coatings. This article will provide a detailed overview of the test, its significance, and its implementation. Cyclic corrosion testing is a method that simulates the natural environmental conditions that materials and products may encounter over an extended period. This technique is carried out in a controlled laboratory environment to accelerate and replicate the effects of natural weathering.

The GMW14872 cyclic corrosion laboratory test plays a vital role in the automotive industry, providing accurate and reliable results on the durability and corrosion resistance of materials and coatings. By adhering to this standard, manufacturers can improve the quality and longevity of their products, leading to increased customer satisfaction and reduced maintenance costs. GMW14872 is a standard developed by General Motors (GM) that outlines the requirements and procedures for conducting cyclic corrosion laboratory tests. This standard ensures consistency and reliability in evaluating the performance of automotive materials and coatings.

SAE J2334 Laboratory Cyclic Corrosion Test
Equipment Model WEW-CCT-500L WEW-CCT-800L WEW-CCT-1500L
Inside Capacity, Liters 500 L 800 L 1500 L
Interior Dimensions (W x D x H mm) 1100*750*600 1300*1000*600 2000*1000*700
Exterior Dimensions (W x D x H mm) 1850*1150*1700 2000*1400*1750 2800*1400*1750
Web-Browser Control/Service Ethernet Port Ethernet Port Ethernet Port
Parking Style Floor Type Floor Type Floor Type
Temperature Fluctuation ±0. 5℃ ±0. 5℃ ±0. 5℃
Temperature Uniformity ±1.5℃ ±1.5℃ ±1.5℃
Internal External Material Reinforced Polyester Resin Reinforced Polyester Resin Reinforced Polyester Resin
Power Source AC230V ±10% 50HZ 2/N/PE AC230V ±10% 50HZ 2/N/PE AC230V ±10% 50HZ 2/N/PE
Max Power Consumption 3.5 kW 4.5 kW 5.7 kW
Max Current 16 A 21 A 25 A
Environmental Operation Temperature 23℃±5℃/≤85%RH 23℃±5℃/≤85%RH 23℃±5℃/≤85%RH
Net Weight 225 Kgs 290 Kgs 350 Kgs
The complex salt solution in percent(%) by mass shall be as specified asfollows:
Sodium Chloride (NaCI): 0.9%.Calcium Chloride (CaClz):0.1%.
Sodium Bicarbonate (NaHCO3): 0.075%.
4.1.1 Salt Solution Preparation. 4.1 Preparation. Test Procedure
Sodium Chloride must be reagent grade or Morton Culinox 999 Food grade. Calcium Chloride must be reagentgrade. Sodium Bicarbonate must be reagent grade (e.g., Arm and Hammer Baking Soda or comparable productis acceptable). Water (H2O)must meet ASTM D1193,Type lV requirements.
Note:Either CaCl or NaHCOs material must be dissolved separately in water and added to the solution of theother materials. lf all solid materials are added dry, an insoluble precipitate may result.
Salt solution makeup calculator for the appropriate amount of NaCI, CaCl2, NaHCO3, and H:0 examples areshown in Appendix B,Figures B1 thru B6.
Additional contaminants (dust, grit, poultice, and exhaust condensate) called out in the Deviations Section aredefined in Appendix C thru Appendix F.
Corrosion coupons should be cleaned using a commercial grade degreaser solutionand accurately weighed prior to use.The weight, in grams (g), shall be recorded and retained for future reference.lf coupons are not used immediately, coupons should be stored such that the coupons are corrosion free at theStart-of-Test (sOT). 4.1.2 Coupon Preparation.
lt is critical that all forming and/or preservation oils/ubes be removed prior to exposure to allow forgeneral/uniform corrosion of the coupon.This process can be aided by using a commercial grade degreaserprior to methanol or acetone clean.
Prior to start of test;prepare the coupon rack with sufficient coupons tomonitor the test.The number of coupons recommended for different test durations are shown in Appendix A,Table A4. 4.1.3 Coupon Rack Preparation.
The exact location of each coupon on the rack shall be identified and recorded using the pre-stamped numbersfor reference as illustrated in Appendix A,Figure A4.
Allow a minimum 5 mm spacing between the coupons and the rack surface. All coupons shall be securedvertically with no more than 15 degree deviation from vertical and must not contact each other.
The coupon rack shall be placed in the general vicinity of the test samples being tested, such that the couponsreceive the same environmental exposure as the test samples.
Note: Mass loss coupons are test monitoring devices and are not intended to be exposed to additional stresseswhich may be added to the base test (i.e., gravelometer, dust, grit, exhaust condensate, thermal exposure, etc.)Additional coupons may be required to monitor special test conditions (refer to Deviations Section).
Not applicable. 4.2.1 Environmental Conditions.  4.2 Conditions.
Deviations from the requirements of this standard shall have been agreed upon. Suchrequirements shall be specified on component drawings, test certificates, reports, etc. 4.2.2Test Conditions. 
See Appendix A, Figure A1 for the steps that comprise the test method. Repeat the cycledaily, as necessary, until the test exposure requirements are met.At the option of the test requestor, the testcan be continued throughout weekends to decrease the overall test time provided that the number of cycles andmass loss requirements are met. 4.3.1 Test Execution.  4.3 Instructions.
For each salt mist application, use the spray apparatus to mist the samples and couponsuntil all areas are thoroughly wet/dripping. The quantity of spray applied should be sufficient to visibly rinse awaysalt accumulation left from previous sprays. The first salt mist application occurs at the beginning of the ambientstage. Each subsequent salt mist application,when specified,should occur approximately 1.5 h after the previous application in order to allow adequate time for test samples to dry. A minimum of 1 h spacing betweenthe end of a previous salt application and the subsequent salt application is required. 4.3.2 Salt Application.
The test may be modified to target specific component applications.Refer to DeviationsSection. 4.3.3 Test Options.
Corrosion coupons shall be removed and analyzed after a predetermined number ofcycles (typically five (5)) throughout the test to monitor the corrosion (less frequent for longer exposures, i.e.,>40 cycles).To analyze coupons,remove one (1) coupon from each end of the rack,clean to prepare forweighing, and an average mass loss determination.Although corrosion rate may vary somewhat during theduration of the test, an assumption of linearity may be useful in predicting the number of cycles to meet futuremass loss targets. 4.3.4 Test Monitoring. 
4.3.4.1Before weighing, clean the coupons using a mild sand/bead blast (550 ±70)kPa(80±10) psi) processto remove all corrosion by-products from the coupon surface. 
4.3.4.2 Compare the actual mass loss to the targeted value. Refer to Appendix A, Table A1,Table A2 orTable A3for targeted mass loss values, in grams, for various test exposures as a function of the coupon’s originalthickness. Testing should be conducted as necessary to achieve necessary coupon mass loss. The number ofcycles required to achieve required mass loss must meet that defined in Appendix A, Table A1 for Method 1,Table A2 for Method 2 and Table A3 for Method 3.
Note: Coupon mass loss targets corresponding to incremental test exposures are not included in Appendix A,Table A1,Table A2 or Table A3. The processes defined in 4.3.4 and 5.3.1 may be used to check test progressand assure that the test is being run correctly.Corrosion mass loss should increase consistently betweendocumented exposure values. If the actual mass loss does not fall within the targeted range for the specifiedexposure(s) as listed in Appendix A, Table A1,Table A2 or Table A3, then the test should be repeated. Also, thereasons why the test did not fall within the target range should be investigated and corrected before resumingthe test.
Temperature and humidity ramp times between the ambient stage and humid stage,and between the humid stage and dry stage , can have a significant effect on test acceleration.(Corrosion ratesare highest during these transition periods.)Typically, the time from the ambient stage to the humid stage shouldbe approximately 1 h and the transition time between humid stage and dry stage should be approximately 3 h.These ramp times can be adjusted to increase or decrease test acceleration in order to meet targeted massloss. Any significant deviation from the ramp time described should be documented with the test results andrequires prior approval by the parties concerned. Ramp time is to be included as part of the specified exposureperiod. 4.3.5 Test Acceleration.
For any periods of extended downtime (i.e. >(4 to 5) d ), it is recommended thattest parts and associated coupons receive a freshwater rinse prior to the downtime period and are stored inambient conditions to help minimize corrosive effects during this time. If downtime exceeds or is expected toexceed 17 consecutive days, this condition should be reviewed with test requestor. Additional special measuresmay be required to control the corrosion behavior of the test samples during this period.Storage in a desiccator,freezer, etc., may be appropriate. Extended downtime periods and any associated special measures should beincluded in the test documentation. 4.3.6 Extended Downtime.
The test sample(s) shall be inspected for corrosion by means ofGMW15356,GMW15357,GMW15358,GMW15359,and photographed (as necessary) at the end ofpredetermined cycles. Samples may be rated in terms of percent corroded area per ASTM D610 or some othercomparable standard if agreed upon by test requestor and tester. lf test samples containing plastic materials arebeing tested, any discoloration or degradation and/or adhesive bond failure (delamination) shall be noted and recorded. 4.4 Cosmetic Corrosion Inspection. 
lf scribing is required, on test samples, follow the method described in GMW15282.This method includesmeasurement of corrosion creepback from a scribe line. This method should be used when reporting test resultsunless stated otherwise on drawings or agreed upon by test requestor and tester.
At EOT, the samples shall be rinsed with fresh tap water andallowed to dry before evaluating.EOT functional analysis may involve sectioning, microscopic analysis and/orremoval of corrosion product to determine degree and extent of base metal attack. 4.5 End-of-Test(EOT)Functional Inspection. 
In addition to providing a comprehensive evaluation of corrosion mechanisms, The GMW14872 cyclick corrosion laboratory test also offers insights into synergistic effects arising from temperature, mechanical and electrical cycling, and other environmental stresses. By simulating real-world conditions in a controlled laboratory environment, this test enables the identification of potential weaknesses in assemblies and components, allowing for targeted improvements in materials and design.

Furthermore, The tailored nature of the test exposure/conditions facilitates the replication of specific environmental scenarios, ensuring that the resulting data is directly applicable to diverse real-world settings. This approach not only enhances the efficiency of product development and quality control but also serves as a crucial tool for ensuring the longevity and reliability of critical infrastructure and consumer products. The adaptability and precision of this corrosion testing method make it an indispensable asset for industries reliant on durable and resilient materials.

GMW14872 Cyclic Corrosion Laboratory Test
Laboratory (preferably with controlled ambient conditions). 3.1 Facilities.  Test Resources
3.1.1 Calibration. The test facilities and equipment shall be in good working order and shall have a valid calibration label.
3.1.2 Alternatives. Alternative test facilities and equipment may also be used. However, all measuring variables as specified in this standard shall be determined correctly with respect to their physical definition.
The apparatus for the ambient stage shall have the ability to maintain the following environmental conditions:
• Temperature: (25 ± 3) °C.
• Humidity: (45 ± 10)% Relative Humidity (RH).
• Duration: Approximately 8 h per cycle.
3.2.1 Ambient Stage.  3.2 Equipment.
The apparatus for the humid stage shall have the ability to ramp to (within 1 h) and maintain (for approximately 7 h) under the following environmental conditions:
• Temperature: (49 ± 2) °C.
• Humidity: Approximately 100% RH.
• Duration: Approximately 8 h per cycle.
3.2.2 Humid Stage. 
The apparatus shall consist of a fog/environmental chamber, suitable water supply conforming to ASTM D1193, Type IV, provisions for heating the chamber, and the necessary means of control.
3.2.2.1 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(s) 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 fog 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 2 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 cm 2 . Where samples cannot be read immediately upon completion of the humid stage, closed cell foam balls can be used in combination with the collection funnels (i.e., foam ball in mouth of funnel) to allow moisture to collect while minimizing evaporation.
3.2.2.2 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.
3.2.2.3 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.
The apparatus for the dry off stage shall have the ability to ramp to (within 3 h) and maintain (for approximately 5 h) under the following environmental conditions:
• Temperature: (60 ± 2) °C.
• Humidity: ≤ 30% RH.
• Duration: Approximately 8 h per cycle.
3.2.3 Dry Off Stage. 
The apparatus shall also have sufficient air circulation to prevent temperature stratification, and also allow thorough drying of the test samples.
The solution shall be sprayed as an atomized mist and should be sufficient to rinse 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. 3.2.4 Salt Mist Application. 
Note: The force/impingement from this salt application should not remove corrosion or damage coatings/paints system of test samples.
Coupons serve to monitor the average general bare steel corrosion produced by the test environment. Coupons consist of 25.4 mm wide × 50.8 mm long × 3.18 mm thick pieces of bare SAE 1008-1010 carbon steel, cold-rolled steel per SAE J2329, CR1E (see 7.2), uncoated, no post coating treatment, which are stamped with an alphanumeric identification number (reference Appendix A, Figure A2). 3.2.5 Corrosion Coupons and Mounting Hardware. 
The coupons shall be secured to an aluminum or nonmetallic coupon rack with fasteners as shown in Appendix A, Figure A3 and Figure A4. The bolt, nut, and washers shall be made from a non-black plastic
material, preferably nylon. Appendix A, Figure A4 shows a completed coupon rack configuration. The number of coupons recommended for different test durations are shown in Appendix A, Table A4.
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.   3.3 Test Vehicle/Test Piece. 
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 of (20 ± 5) degrees from vertical.  
3.3.1 Preconditioning of Test Samples. The gravelometer and/or a scribing tool can be used to provide damage to coating layers prior to testing in order to better represent potential in-service damage when appropriate. The use of either of these preconditioning methods shall be agreed upon by the parties concerned and shall conform to the methods described in GMW14700 and/or GMW15282.  
See cycle times in Appendix A, Table A1, Table A2 or Table A3. 3.4 Test Time. 
Not applicable. 3.5 Test Required Information. 
Test technician familiar with test facilities and equipment. 3.6 Personnel/Skills. 
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
related page logoCyclic Corrosion Test Chamber → Machine Detail Pictures → WEW-CCT-500D → Wewon Environmental Chambers Co., Ltd.
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