The salt spray test:
corrosion test for metals

Through continuous spraying with a sodium chloride solution in a climate chamber, corrosion formation is accelerated and the corrosion resistance of a material can be checked.

There are various standards describing the salt spray test. The most well-known are NEN EN ISO 9227, ASTM B117 and DIN 50021.

Would you like to check the corrosion resistance of your coating using the Salt spray test?

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Three variants of the salt spray test

The neutral salt spray test
This variant is used on almost all metals, with or without coating. A 5% sodium chloride solution, a temperature of 35°C and a pH of 6.5 to 7.2 are used.

The acetic acid salt spray test
Frequently used for testing decorative coatings made of copper-nickel-chrome or nickel-chrome. It is also widely used for organic coatings on aluminium (as also prescribed in Qualicoat). The difference compared to the neutral salt spray test is that the salt solution is acidified to pH 3.1-3.3 by adding glacial acetic acid.

The copper-accelerated acetic acid salt spray test
The so-called CASS variant, like the acetic acid salt spray test, is widely used for testing decorative coatings made of copper-nickel-chrome or nickel-chrome and sometimes on coated or anodised aluminium. The process is similar to that of the ASS, but with the addition of 0.26 grams/litre CuCl2*2H2O and a temperature of 50°C.

Do you want to test your product according to ISO 9227 or ASTM B117 standards?

The salt spray test meets the following quality standards

The standards NEN EN ISO 9227, ASTM B117 (previously also DIN 50021) describe the salt spray test. DIN 50021 was already withdrawn in 1988. These standards are virtually identical in terms of execution. The difference between ISO 9227 / DIN 50021 and ASTM B117 is that the samples are placed at an angle of 15° to 25° instead of the 15° to 30° used in ASTM B117.

Working method

The test is usually conducted on panels made from the material to be researched and measuring approximately 150 x 100 mm. These test panels are placed in the climate chamber at an angle of ±20° relative to vertical. In the case of organic coatings, often a scratch measuring 1 or 2 mm in width is made.

A solution of 5% sodium chloride is then continuously sprayed over the test panels at a fixed temperature. The equipment is set such that 1.5 ± 0.5 ml liquid descends per hour onto 80 cm2.

Bigger products

At M2LAB, not only can you have salt spray tests conducted on test panels but entire products can also be tested. Here at M2LAB, we have an XXL salt spray test, specially for large products. Products with a dimension up to 3 metres and a weight of 1,000 kg can be tested in their entirety.

Salt spray test duration

The length of the test depends on the needs of the application. ISO 12944-6 gives guidelines for various “durability ranges”. The test duration in these guidelines varies between 48 and 2,160 hours.

Would you like to know what the appropriate test duration is for your application? We would be happy to advise you about this.

Reporting and advice

For the evaluation of samples with organic coatings, ISO 4628 is often followed, in which rust formation, blistering, and undermining are the key criteria. With organic coatings, we usually see that the quantity of white rust, optical defects, or red rust formation is used as a criterion.

Call +31 (0)13 – 463 06 88 for more information about the lead times for your required laboratory tests.

Would you like to know which test is most suitable for your product?