ISO 9227 Salt Spray Tests
Key facts
| Test | Solution | pH | Chamber temperature |
|---|---|---|---|
| NSS — neutral salt spray | 5% NaCl | 6.5–7.2 | 35 °C (95 °F) |
| AASS — acetic acid salt spray | 5% NaCl + acetic acid | 3.1–3.3 | 35 °C (95 °F) |
| CASS — copper-accelerated acetic acid salt spray | 5% NaCl + acetic acid + copper(II) chloride | 3.1–3.3 | 50 °C (122 °F) |
The three tests
NSS is a neutral 5% sodium chloride fog at 35 °C, used for most metals and coatings.
AASS acidifies the same solution with acetic acid, which speeds up attack on decorative and protective coatings.
CASS adds copper(II) chloride to the acidified solution and runs hotter, at 50 °C. It is the most aggressive of the three.
Reading the result
A result must name the test — NSS, AASS or CASS — as well as the substrate, film thickness and failure criterion. PG-S1’s figures show why: ≥ 2,000 h NSS, ≥ 800 h AASS and ≥ 350 h CASS are three results from three different tests, not a ranking.
Limits
Like ASTM B117, ISO 9227 tests are continuous and never dry, so they rank coatings under one set of conditions. They do not convert into years of service.
Is ISO 9227 NSS the same as ASTM B117?
They are very similar in principle — 5% sodium chloride fog at 35 °C — but they are separate standards with their own detailed requirements. Report which one was used.
How does GB/T 10125 relate to ISO 9227?
GB/T 10125 is the Chinese national standard adopted from ISO 9227 and covers the same three tests. PG-S1 results are reported to GB/T 10125-2021.
Tell us the equipment, the site and the destination port. We reply within 24 hours.