GM 9540P Accelerated Corrosion Test
In 1991 a joint task force from the Society of Automotive Engineers (SAE) and the American Iron and Steel Institute (AISI) evaluated 13 accelerated corrosion tests and concluded that GM 9540 best predicts the cosmetic corrosion of cold rolled steel. This study is among the reasons that GM 9540 has gained popularity as a laboratory corrosion test for steel.
UDRI has five Q-Fog cabinets in which we can perform GM 9540P – Accelerated Corrosion Tests. The tests are covered under our ISO 17025 scope of accreditation which is certified by Laboratory Accreditation Bureau (L-A-B). We take pride in operating the corrosion cabinets in a uniform manner. Our quality control includes operating the chamber with a continuous spray for a minimum of 24 hours before the test begins and using 5 fog collectors (100-mm funnels with the stems inserted in 100 ml graduated cylinders) in the test chamber. The chamber pressure and flow rates are adjusted to produce a 1 to 2 ml per hour collection rate in each collector. As an extra measure to obtain uniform exposure, test panel positions are rotated within the chamber once per week.
The test itself consists of alternate wet and dry cycles where a precisely prepared solution of NaCl, CaCl2, and NaHCO3 are used for the wet cycles. The temperature of chambers are controlled and monitored in accordance with the standard’s protocol. Normally one cycle is completed each day, with the samples sitting undisturbed after the dry bake cycle until the start of the next work day. Cycles are continued until the agreed upon exposure duration is achieved.
UDRI can use its standard protocol to rate exposed samples or we can modify our procedures to meet your specific needs. To evaluate corrosion on scribed panels, our standard procedure calls for skilled technicians to remove the panels from the chamber and rinse them with water while scrubbing with a stiff bristle brush to remove undercut paint. They then evaluate each panel to ensure that all undercut paint has been removed. If some remains, a pick or flat spatula is used to gently remove it. Corrosion at and near the scribe are measured using a protocol derived from GM 9102P. If blistering is observed, it is reported using the rating scale found in ASTM D 714.
If you would like a quote on how much it would cost to test your samples, please contact UDRI's Bill Culhane or call 937-255-0955.
Other Corrosion Testing Available:
ASTM B 117 Salt Spray (Fog)
ASTM G 85-A5: Standard Practice for Modified Salt Spray (Fog) Testing (Prohesion)
NAS 1534: Filiform Corrosion