GMW 14872 CYCLIC CORROSION TESTING
The engineering team that developed GMW 14872 participated in the foundational research and validation of the SAE J2334 standard along with Auto Technology engineering. Armed with those field-proven learnings, they modernized the automotive testing world by updating and eventually replacing old-school protocols like GMW 9540P.
The result was an advanced cyclic corrosion method designed to simulate the lifecycle of specific components. Because different parts of a vehicle experience radically different real-world conditions, GMW 14872 features a massive matrix of exposures and tailoring options based on precise assembly and component placement—whether a part is tucked underhood with varying levels of splash protection, exposed to underbody abuse, or sealed behind the weather stripping.
It’s a complex method, and it frequently shows up in defense applications, aerospace engineering, and rigorous industrial quality programs.
Running it repeatably and correctly requires a chamber that can handle the chaos of a shifting environment.
Learn more about Auto Technology X Series and A Series cyclic corrosion chambers.
GMW 14872 Phases and Validation
GMW 14872 consists of multiple 24-hour cycles that move samples through ambient drying, controlled electrolyte wetting, high-temperature and high-humidity exposure, and high-temperature dry-off, with separate weekend dwell requirements. Corrosion coupons are positioned near the samples and exposed to the same temperature, humidity, and solution conditions so their measured mass loss can verify that the chamber delivered the required corrosion severity for the applicable vehicle location and method.
1. The Ambient Phase
The ambient phase calls for a target environment of 25 ± 3°C and 45 ± 10% relative humidity (RH) for approximately 8 hours. Crucially, the spirit of this standard intends for this step to be run naturally, not artificially.
This design choice throws back to the original manual testing protocols performed on open racks at GM facilities, where technician-applied sprays were allowed to dry off via ambient laboratory air.
Auto Technology chambers give you two distinctly advanced engineering methods to achieve this compliance:
The Thermodynamic Reality: Open Air
Auto Technology chambers feature computer-controlled, automated air cover lifters. At the onset of the ambient stage, the system automatically opens the lid to expose the samples directly to the room volume.
Instead of artificially forcing air across the samples, this method allows the sample surfaces to cool and dry via natural convection and radiation. Energy transfers strictly through passive atmospheric exposure.
The Managed Route: Internal Climate Control
If your testing facility suffers from seasonal temperature swings, baseline humidity issues, or drafts, opening the lid isn’t practical.
For these environments, Auto Technology offers advanced climate control packages that can artificially synthesize an ambient atmosphere completely within a closed chamber environment.
Automated Cover Lifters in Action
2. The Wetting Step
In most cases, GMW 14872 requires a specific 1% by mass complex electrolyte solution. You are mixing 0.9% sodium chloride (NaCl), 0.1% calcium chloride (CaCl2), and 0.075% sodium bicarbonate (NaHCO3) into ASTM D1193 Type IV water.
Premixed GMW 14872 Solution
Auto Technology supplies a premixed electrolyte solution for running GMW 14872.
View GMW 14872 Premixed Solution →The application of the solution must be heavy enough to leave the samples and corrosion coupons thoroughly wet and dripping, and subsequent applications must be sufficient to physically rinse away any salt accumulation left behind by previous cycles. However, the force and impingement need to be controlled so that they do not remove corrosion or damage the coating or paint system of the samples.
GMW 14872 mandates that the spray application thoroughly wet all focal areas of the sample. The orientation of the spray mechanism must target the specific in-service orientation of the production sample to mimic real-world field splash.
The first application occurs at the beginning of the ambient phase. If the specific sample area and method call for multiple applications, each subsequent salt application should occur approximately 1.5 hours after the previous application to allow adequate time for the samples to dry. The standard mandates a minimum of 1-hour spacing between the end of a previous salt application and the subsequent application.
To meet the constraints of precise targeting and saturation without high-pressure impingement, Auto Technology chambers leverage specialized adjustable, low-velocity, high-volume cascading nozzles.
The solution is pulled from the built-in 60-gallon reservoir via a dedicated solution spray pump. This allows you to calibrate the orientation to your exact part geometry, ensuring perfect cycle-to-cycle automation of the method’s wetting requirements.
GMW 14872 Cascading Spray in Action
3. The High-Temperature and High-Humidity Phase
The method transitions to the humid stage, ramping within an hour to 49 ± 2°C and approximately 100% RH. The standard explicitly notes that visible water droplets must form on the samples to confirm proper wetness.
Auto Technology chambers can achieve this deep, uniform saturation through a heated wet bottom combined with precision-regulated water fog generation.
The wet bottom fills with water directly over the internal titanium heater rods, generating a thick, stable humidity layer from the bottom up, while the Uni-Fog dispersion towers maintain the required 0.75 mL/h to 1.5 mL/h collection rates from above.
High Humidity Inside an Auto Technology Chamber
4. The High-Temperature Dry-Off Phase
The dry-off phase is a 3-hour ramp to 60 ± 2°C and a bone-dry humidity ceiling of ≤30% RH. Striking a target that low while the interior walls are covered in condensation is incredibly tough for a standard cabinet.
Auto Technology chambers tackle this by activating a rapid drain system to empty the wet bottom. Simultaneously, the internal heaters fire up while a heavy-duty air-exchange system goes into action.
This continuous air-circulation and heat combination thoroughly dries the samples right on schedule.
GMW 14872 Corrosion Coupons
GMW 14872 Mass-Loss Panels
Auto Technology supplies standardized mass-loss panels for monitoring the severity of a GMW 14872 exposure.
View GMW 14872 Mass-Loss Panels →In GMW 14872, the overall exposure is dictated by a targeted coupon mass loss rather than just running the method for a set number of days.
Coupons serve to monitor the average general bare-steel corrosion produced by the corrosion chamber, providing verification that the correct amount of environmental acceleration has been delivered. Mass-loss coupons are strictly monitoring devices.
The coupons and rack must be placed in the general vicinity of the samples being evaluated. This ensures that the corrosion coupons receive the same environmental, temperature, and solution exposure as the samples.
GMW 14872 and GMW 9540P Corrosion Coupon Rack
Auto Technology supplies a purpose-built rack for consistently positioning GMW 14872 corrosion coupons within the exposure zone.
View the GMW 14872 Coupon Rack →Coupons are pulled periodically throughout the method to monitor ongoing corrosion rates. If the calculated mass loss does not fall within the target ranges specified by the standard for that vehicle location and method, the exposure must be investigated and repeated.
Custom Protocol Design & Testing Solutions
Whether you need to strictly satisfy a Tier 1 automotive contract or adapt cyclic testing to complex industrial specifications, Auto Technology has the engineering infrastructure to support you:
Custom Chamber Manufacturing
We design and build chambers optimized for standard GMW 14872 profiles, as well as customized footprints for massive walk-in assemblies.
Learn more about Auto Technology cyclic corrosion chambers →Galvanic Corrosion Focus: Option 6
If you are evaluating mixed-metal joints or assemblies prone to galvanic acceleration, Auto Technology chambers can be optioned with the hardware necessary to run specialized deviations like Option 6.
This includes heavy-duty internal pumps and plumbing designed to handle the abrasive, high-salinity fireclay-and-salt slurries required to evaluate real-world galvanic breakdown.
Accredited Testing Services
Don’t have the floor space or capital budget to bring a cyclic chamber in-house just yet? Auto Technology’s certified, fully accredited testing laboratory can run GMW 14872 on your samples.
Our testing experts can work alongside your engineering group to design custom, accelerated diagnostic programs tailored to identify your specific product failure modes.
A2LA-Accredited Proficiency Testing Programs
If your laboratory is already accredited, regular participation in a GMW 14872 Proficiency Testing program may be a strict requirement to maintain your standing.
Auto Technology Company is an accredited Proficiency Testing Provider, ensuring your GMW 14872 operator and chamber data are analyzed, benchmarked, and validated by true corrosion professionals.
Explore Auto Technology Proficiency Testing →GMW 14872 Frequently Asked Questions
What is GMW 14872?
GMW 14872 is an accelerated laboratory cyclic corrosion method used to evaluate assemblies and components. It combines salt spray applications, ambient exposure, high-temperature and high-humidity conditions, and high-temperature dry-off to accelerate general, galvanic, crevice, and other corrosion mechanisms.
Is GMW 14872 run the same way for every component or assembly?
No. GMW 14872 is tailored according to the component or assembly, its vehicle area, mounting location, level of splash protection, intended cosmetic or functional evaluation, selected Method, required Exposure, and any specified deviation.
An underbody component, an underhood component protected from splash, an exterior panel, a secondary surface, and an interior component may require different salt spray frequencies, coupon mass-loss targets, and cycle ranges.
How is the correct GMW 14872 configuration selected?
The applicable engineering documentation must identify the vehicle area and mounting location, Method 1, Method 2, or Method 3, the required cosmetic or functional Exposure, the number of salt spray applications, and any applicable deviation.
The acceptance criteria must also be defined in the relevant material specification, drawing, Vehicle Technical Specification, Subsystem Technical Specification, Component Technical Specification, Statement of Requirements, or other engineering documentation.
What do Exposures A, B, C, D, and E represent?
Exposure A is used for underbody components. Exposure B is used for underhood components. Exposure C is used for exterior components and panels, secondary surfaces, and interior components. Exposures D and E are used for functional assessment across component types.
Exposure 0 represents the initial-delivery or 0-year condition and is evaluated using two cycles of the exposure associated with the applicable vehicle area and mounting location.
What do Method 1, Method 2, and Method 3 change?
Method 1, Method 2, and Method 3 establish different combinations of coupon mass-loss targets and permitted cycle ranges for particular vehicle areas, mounting locations, and exposure levels.
The required Method must be identified in the applicable material specification, drawing, or other engineering documentation. A laboratory should not select the Method based only on convenience or available chamber time.
What phases are included in a GMW 14872 cycle?
One cycle is 24 hours and generally includes an approximately 8-hour ambient stage, an approximately 8-hour humid stage, and an approximately 8-hour dry stage.
Salt spray and any additional specified stresses are applied according to the selected component location, Method, Exposure, and test option. Weekend and holiday conditions are maintained at no more than 35°C and 55% relative humidity unless the method is continued through the weekend.
What are the GMW 14872 ambient-stage conditions?
The ambient stage is maintained at 25 ± 3°C and 45 ± 10% relative humidity for approximately 8 hours per cycle.
The first salt spray application occurs at the beginning of the ambient stage. When additional applications are required, they are spaced to allow the samples to dry between sprays.
What are the GMW 14872 humid-stage conditions?
The humid stage ramps to 49 ± 2°C within approximately 1 hour and operates at approximately 100% relative humidity for an approximately 8-hour total stage.
When wet-bottom or steam-generated humidity is used, visible water droplets must form on the samples to verify proper wetness. When water fog is used, the fog must be directed or baffled to minimize direct impingement on the samples.
What are the GMW 14872 dry-stage conditions?
The dry stage ramps to 60 ± 2°C within approximately 3 hours and operates at no more than 30% relative humidity for an approximately 8-hour total stage.
The chamber must provide enough air circulation to prevent temperature stratification and thoroughly dry the samples.
What salt solution is used for GMW 14872?
The standard complex salt solution contains 0.9% sodium chloride, 0.1% calcium chloride, and 0.075% sodium bicarbonate by mass in water meeting ASTM D1193 Type IV requirements.
Additional contaminants may be required when a specified deviation calls for dust, grit, poultice, exhaust condensate, or another added stress.
How must the GMW 14872 salt spray be applied?
The salt solution must be sprayed directly onto the samples and corrosion coupons until all required areas are thoroughly wet and dripping.
Each application must be sufficient to visibly rinse away salt accumulation left from previous sprays, but the spray force must not remove corrosion products or damage the coating or paint system.
How often is the GMW 14872 salt spray applied?
Salt spray frequency depends on the vehicle area, mounting location, level of splash protection, selected Method, and required Exposure.
Some applications require four sprays per cycle, some require one spray per cycle, and protected secondary-surface or interior locations may require one spray every five cycles. The first spray occurs at the beginning of the ambient stage.
How are multiple salt spray applications spaced?
When multiple applications are required, each subsequent spray should occur approximately 1.5 hours after the previous application to allow the samples to dry.
A minimum of 1 hour is required between the end of one salt spray application and the beginning of the next application.
How should samples be positioned during GMW 14872?
Representative production samples should be oriented to reproduce their known in-service orientation whenever possible.
When panels are used or the in-service orientation is unknown, the sample should generally face upward at an angle of 20 ± 5 degrees from vertical.
Why are corrosion coupons used in GMW 14872?
Corrosion coupons monitor the average general bare-steel corrosion produced by the chamber and verify that the required amount of environmental acceleration has been delivered.
GMW 14872 does not rely on elapsed time alone. The applicable coupon mass-loss target must be achieved, and it must be achieved within the cycle range specified for the selected Method, component location, and Exposure.
Where should GMW 14872 corrosion coupons be placed?
The coupon rack must be placed in the general vicinity of the samples so that the coupons receive the same base environmental exposure as the samples.
The coupons are monitoring devices and are not normally subjected to additional stresses such as gravel, dust, grit, exhaust condensate, or separate thermal exposure unless additional coupons are specifically required for those conditions.
How often are GMW 14872 corrosion coupons evaluated?
Coupons are removed and analyzed after predetermined intervals, typically every five cycles, although longer exposures may use less frequent checks.
One coupon from each end of the rack is cleaned and weighed, and the average mass loss is used to monitor progress toward the applicable target.
What happens if coupon mass loss is outside the required range?
The reason for the incorrect corrosion rate must be investigated and corrected. If the actual coupon mass loss does not fall within the target range for the specified exposure, the exposure should be repeated.
The required mass loss must also be reached within the number-of-cycles range specified for the applicable Method, vehicle area, mounting location, and Exposure.
Does completing GMW 14872 prove that a component will pass its functional requirement?
No. Different corrosion mechanisms accelerate at different rates, and completing the required exposure does not by itself prove that a component satisfies every functional requirement.
A comprehensive failure-mode analysis and the applicable engineering acceptance criteria are still required to determine whether the component meets its expected service life.
Can GMW 14872 include additional mechanical, thermal, electrical, or contaminant stresses?
Yes. The method may be modified to represent specific component applications, including additional temperature, mechanical, electrical, contaminant, and other stresses.
These options and deviations must be agreed upon in advance and documented in the applicable engineering requirements and final report.
Can Auto Technology chambers support GMW 14872 Option 6?
Yes. Auto Technology chambers can be configured with the heavy-duty pumps and plumbing required to handle the abrasive, high-salinity fireclay-and-salt slurry associated with the Option 6 galvanic corrosion deviation.
Does Auto Technology provide GMW 14872 laboratory services?
Yes. Auto Technology’s accredited laboratory can run the applicable GMW 14872 Method, Exposure, salt spray schedule, and documented deviations on customer samples.
The required vehicle area, mounting location, splash protection, cosmetic or functional objective, acceptance criteria, and engineering callout should be identified before the work begins.
Does Auto Technology offer GMW 14872 proficiency testing?
Yes. Auto Technology Company is an accredited Proficiency Testing Provider. Its GMW 14872 Proficiency Testing program can be used to analyze and benchmark laboratory operator and chamber performance.
Learn more about Auto Technology Proficiency Testing programs.