Selecting the correct corrosion standard is an important part of specifying HVAC coil coatings, particularly in environments where an extreme coastal HVAC coating is needed. For over 100 years, ASTM B-117 had been widely recognized as the “gold standard” in corrosion testing – at least until the introduction of ISO 20340. Now that ISO 20340 has been renamed ISO 12944-9, engineers finally have an ISO standard that more accurately addresses HVAC coil corrosion protection in extreme offshore environment constructions.

Why does ISO 12944-9 provide a more accurate test result than ASTM B-117?

ASTM B-117 tests coatings against a continuous salt spray. Since the procedure was first introduced in 1939, the test has been conducted for increasingly longer and longer exposure periods. Some tests now run for 15,000 – 20,000 hours, which is the equivalent of 20+ months of continuous exposure to the exact same salt spray environment. Although it might seem obvious that no real-world environment remains perfectly consistent for nearly two years, in 1995 The Society for Protective Coatings (SSPC) studied ASTM B-117 and published a paper that concluded that the ASTM B-117 test was an “unreliable means for predicting coating behavior.

ISO 12944-9 (formerly known as ISO 20340) uses a cyclic test where the test subject is exposed to 25 one-week cycles of common extreme coastal environment conditions. Each cycle consists of 72 hours of UV exposure, 72 hours of salt spray, and 24 hours of freezing. This cyclic method of testing correlates far better to the real-world environment HVAC coils will experience while in service. In addition, ISO 12944-9 has combined the C5-I (very highly corrosive, industrial) and C5-M (very highly corrosive, marine) environments into a new environmental corrosivity category – CX (extreme). The new CX Extreme environment provides a standard for atmospheric conditions that result in greater mass loss per unit surface/thickness loss after first year of exposure than the previous C5 environments.

Learn more about the differences between ASTM B-117 and ISO 12944-9 »

Fortunately, Heresite tests against both B-117 and ISO 12944-9. We can provide B-117 test results up to 18,000 salt spray hours for P-413, 3,500+ hours for ES-600, and 2,000 hours for VR-514. However, we strongly encourage engineers to specify coatings that can pass the ISO 129449-9 standard, because the performance of the product in use will be far more predictable given the more realistic testing environment. Both Heresite’s P-413 and ES-600 have passed the 25-week (4,200 hour) ISO 12944-9 test. Learn more about Heresite’s HVAC-R & Radiator Protective Coatings and compare our products. Still have questions? Feel free to contact us. We’re happy to answer questions and provide you with the data you need to choose the right protective coil coating for your particular needs.


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