What is ISO 9227?

ISO 9227 is a European derivative of the salt spray test developed by the American Society of Testing and Materials (ASTM). ISO 9227 is an excellent reference document for any salt spray testing with additional hints and tips throughout the document.

Test Methodology:

The test involves placing specimens in an enclosed chamber where they are exposed to a continuous indirect neutral saline water, producing a fine fog or mist. The fallout rate is controlled between 1.0 and 2.0 ml per 80 cm² per hour, with the chamber temperature maintained at +35°C & 47°C for saturation tower (depending on NSS, AASS or CASS). Chamber conditions are held at a constant steady state for the duration of the test, which can be varied as required.

Method

Salt spray testing is carried out by placing specimens within a corrosion test chamber that complies with the requirements of ISO 9227, Section 4 (Apparatus), and is operated in accordance with Section 8 (Operating Conditions) of the same standard.

The test solution is prepared by dissolving high-purity sodium chloride in purified water to produce a solution containing 5% sodium chloride and 95% water by mass. The purity / makeup of both the salt and water must match that of the ISO 9227 Standard.

Depending on the test method being employed, the solution is prepared in accordance with Section 3 of ISO 9227. The three principal test variants are:

• NSS (Neutral Salt Spray): The collected solution must maintain a pH between 6.5 and 7.2.
• AASS (Acetic Acid Salt Spray): Glacial acetic acid is added to the salt solution to adjust the pH to between 3.1 and 3.3.
• CASS (Copper-Accelerated Acetic Acid Salt Spray): Copper chloride dihydrate is added to achieve a solution concentration of 0.26 g/L ± 0.02 g/L.

Before the test specimens are introduced, the chamber is stabilised at the specified operating temperature of 35°C and adjusted to produce the required salt fog deposition rate. The fallout rate is verified using a minimum of two collection devices, each consisting of an 80 cm² funnel connected to a graduated measuring cylinder. For each spray atomiser, one collector is positioned close to the atomiser and the other at a more distant location. These collectors are installed at approximately the same height as the test specimens and positioned in accordance with the standard, while also considering the effective working area defined by the chamber manufacturer.

Typical Application of ISO 9227 Testing

This test is commonly used to evaluate the corrosion resistance of coated and uncoated metal components when subjected to a salt-laden atmosphere under controlled elevated-temperature conditions.

Performance is assessed by observing the development of corrosion products, including white rust and red rust, following exposure for a defined period. The duration of testing varies according to the expected corrosion resistance of the material or coating under evaluation. Generally, coatings that provide greater protection against corrosion will require longer exposure periods before any visible signs of oxidation or corrosion are detected.

Typical Application Areas include:

• Automotive
• Aerospace & Defence
• Marine & Offshore
• Electronics
• Coatings / Paints