An Accelerated Salt Spray Test Tailored Towards Automotive OEMs
GMW14872 Cyclic Corrosion Laboratory Test is a widely-practiced modern corrosion test standard that simulates outdoor corrosive conditions experienced by automobiles around the world. The standard builds upon its predecessor, GM9540P, by specifying relative humidity during ambient and dry phases of the test. GMW14872 improves upon the legacy test even further by also specifying ramp times between phases. The standard is performed by many manufacturers serving the automotive sector who need to evaluate the performance of their products against oxidation.
Test Parameters
- Temperature range
- Ambient Stage: 25 °C, 45% RH with intermittent Stress Application (see below)
- Humid Stage: 49 °C, approximately 100% RH (condensing humidity)
- Dry-Off Stage: 60 °C, <30% RH
- Stress Application
- The standard includes several different options for its Stress Application. This may include contamination by way of salt spray or grit, or other stressors such as thermal or mechanical. For the purpose of this summary, we consider the salt solution application as performed in a Q-FOG CRH cyclic corrosion tester.
- Salt Solution (by mass):
- Sodium Chloride (NaCl) 0.9%
- Calcium Chloride (CaCl2) 0.1%
- Sodium Bicarbonate (NaHCO3) 0.075%
- Salt Mist Application:
- Manually or automatically
- Test specimens must be thoroughly wet/dripping
Note: Calcium chloride and sodium bicarbonate must be dissolved separately, or the insoluble precipitate calcium chloride will form
- Corrosion Coupons
- GMW14872 requires continual monitoring of the corrosivity of the chamber by using corrosion coupons. A target mass loss for several different exposure times is included in the standard.
- The standard also includes dimensional specifications for the cold-rolled steel coupon, along with each to be serialized.
- Q-Lab’s CXB-12 Corrosion Coupons are specifically designed for, and satisfy all of the requirements included in, GMW14872.
Why Test to GMW14872
Testing automotive components according to GMW14872 helps validate their performance in corrosive environments. The standard provides guidance for exposure periods of automotive parts mounted in several different locations; underhood, exterior, secondary surface, and even interior. In addition to these different exposure areas, the standard also provides distinction between cosmetic corrosion and functional failure.
Another reason to use GMW14872 as a standard for evaluating materials and assemblies is the long transition periods between dry and wetting conditions. Maintaining a relative humidity in a 50-80% range will accelerate localized corrosion due to the low deliquescence RH% of the calcium chloride salt. The standard even notes that corrosion rates are highest during these periods.
These reasons make GMW14872 one of the most widely-practiced modern corrosion standards used today.
Pros and Cons of GMW14872
- Recreates the same degradation effects seen outdoors for realistic results
- Specifies temperature and relative humidity transitions, improving repeatability and reproducibility.
- Includes significant time at intermediate RH values for optimal outdoor simulation
- Uses corrosion coupons to ensure the test was conducted correctly
- Time consuming - results may take longer than a less sophisticated test like neutral salt spray
- Requires a corrosion test chamber capable of controlled RH and application of shower
- Potentially over-specifies testing when a simpler pass/fail test might suffice
How Q-Lab Can Help
Q-FOG Cyclic Corrosion Test Chambers
Cyclic corrosion tests that include controlled relative humidity provide the best laboratory simulation of natural atmospheric corrosion. Q-Lab’s Q-FOG CRH models can maintain defined temperature and relative humidity values, recreating the same corrosive effects that occurs over several years outdoors.
Testing Services
Q-Lab offers a full range of laboratory testing services in our fully-equipped laboratories in Florida and Germany. We can perform everything from simple salt spray testing to modern automotive cyclic corrosion tests like GMW14872. Laboratory corrosion testing can be used for quality control, material certification, durability studies, and independent third-party verification.
Q-PANEL Standard Test Substrates
Q PANEL paint test substrates are the world’s most recognizable and widely-used standard test panels. Q Lab manufactures millions of panels each year for a variety of industries, with most available immediately from stock. Q Lab’s CXB-12 mass-loss corrosion coupons ensure repeatability and reproducibility when performing GMW 14872.
More GMW 14872 Resources
Standards Tool
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