🧂 Salt spray corrosion test

Automotive PN-EN ISO 9227

Overview

STATUS (as of 02.11.2026). PN-EN ISO 9227:2023-02 — Polish version (published 05.08.2024), implements EN ISO 9227:2022 and ISO 9227:2022 [IDT], replaced PN-EN ISO 9227:2017-06 (English and Polish versions); amendment PN-EN ISO 9227:2023-02/A1:2024-10 — Polish version (published 18.09.2025), implements ISO 9227:2022/Amd 1:2024 and concerns the footnote in 5.2.2 (warning). The catalogue cards carry no withdrawal notice. The fifth ISO edition (11.11.2022) added requirements for the arrangement of test specimens, changed the arrangement of the collecting devices (examples in Annex E), allowed DC04, DC05 and UNS G10080 steels as an alternative to CR4 steel for reference specimens (interlaboratory comparison in Annex F), allowed diluted acetic acid for the AASS and CASS solutions and specified the permitted copper concentration when a cabinet used for CASS is re-used.

SCOPE AND LIMITATIONS (Clause 1, introduction). The standard specifies the apparatus, reagents and procedure for the NSS, AASS and CASS tests for assessing the corrosion resistance of metallic materials with or without permanent or temporary corrosion protection, and the method for evaluating the corrosivity of the cabinet. It does not specify the dimensions or types of test specimens, the exposure period for a particular product or the interpretation of results — these are given in product specifications. The NSS test is particularly applicable to metals and their alloys, metallic coatings (anodic and cathodic), conversion coatings, anodic oxide coatings and organic coatings on metallic materials; AASS and CASS to decorative coatings of copper + nickel + chromium or nickel + chromium, and also to anodic and organic coatings on aluminium. Resistance in salt spray seldom corresponds to resistance in other media; different substrates are not compared directly, comparison makes sense only for sufficiently similar coatings, and the reproducibility of the test — especially for production parts tested in different laboratories — can be low.

SOLUTIONS (Clause 5). Sodium chloride is dissolved in distilled or deionized water with a conductivity not higher than 20 µS/cm at 25 °C to a concentration of 45 g/l to 55 g/l; the solution collected in the cabinet must have (50 ± 5) g/l (specific gravity 1,029–1,036 at 25 °C). The sodium chloride must not contain in total more than 0,005 % of copper, nickel and lead, more than 0,1 % of sodium iodide and more than 0,5 % of impurities in the dry salt; anti-caking agents can act as corrosion inhibitors or accelerators. NSS: pH of the collected solution 6,5–7,2 at (25 ± 2) °C, adjusted with hydrochloric acid, sodium hydroxide or sodium bicarbonate. AASS: addition of glacial acetic acid (at least 99,7 %) or diluted acid (more than 10 %) to a pH of the collected solution of 3,1–3,3 (an initial solution of pH 3,0–3,1 usually ensures this). CASS: in addition copper(II) chloride dihydrate (at least 99,0 %) — (0,26 ± 0,02) g/l, pH as for AASS.

APPARATUS (Clause 6). Components in contact with the spray are made of materials resistant to corrosion that do not influence the corrosivity of the solution. The spray must not fall directly on the specimens, and drops from the upper parts of the cabinet must not fall on them; in cabinets smaller than 0,4 m³ the effect of loading on the distribution of spray and temperature must be considered. The air to the atomizers is filtered, humidified and heated, and the atomizing overpressure is 70 kPa to 170 kPa (typically (98 ± 10) kPa; Table 1 gives guiding values for the water temperature in the saturation tower). The fall-out is checked with at least two collecting devices — funnels 100 mm in diameter (collecting area about 80 cm²) in the specimen zone; for checking the cabinet at least six are used (four corners and two central points), among other times after installation, relocation, repair and an idle period longer than four weeks. A cabinet used for AASS or CASS is not used for NSS before thorough cleaning and checking of the pH of the collected solution.

TEST CONDITIONS. The 1990 edition places flat specimens with the test surface upwards at an angle as close as possible to 20° from the vertical (always between 15° and 30°), so that solution does not drip from specimens onto those below. The available fragments of text do not cover the temperatures and fall-out — according to descriptions by a testing laboratory and a cabinet manufacturer: (35 ± 2) °C for NSS and AASS, (50 ± 2) °C for CASS, fall-out of 1,0 to 2,0 ml/h per 80 cm², specimens at an angle of 15–25°. The corrosivity of the cabinet is checked with steel reference specimens (Clause 7).

WHAT WE DO NOT GIVE HERE. The requirements of Clauses 7–14 of the current edition (evaluation of cabinet corrosivity and its criteria, preparation and arrangement of specimens, operating conditions, recommended test durations, treatment of specimens after the test, evaluation of results, test report) — the available text of the 2022 edition ends at 6.6; the exposure period and evaluation criteria for products — they are set by product specifications.

Method principle

In a closed cabinet an approximately 5 % sodium chloride solution is atomized under controlled conditions: neutral (NSS), acidified with acetic acid (AASS) or acidified with the addition of copper(II) chloride (CASS). The spray does not fall directly on the specimens but settles on them naturally; the rate and concentration of the fall-out are checked with collecting devices in the specimen zone. After the period given in the product specification, the specimens are evaluated according to that specification.

Applications

• Checking that the quality of a metallic material with or without corrosion protection is maintained (quality control)
• Detecting discontinuities, pores and damage in metallic, organic, anodic oxide and conversion coatings
• NSS — metals and alloys, anodic and cathodic metallic coatings, conversion coatings, anodic oxide coatings and organic coatings on metals
• AASS and CASS — decorative coatings of copper + nickel + chromium or nickel + chromium; anodic and organic coatings on aluminium
• Comparison of specimens with the same, sufficiently similar coating — not for ranking different materials or predicting long-term resistance

Key parameters

Standard

Standard number

PN-EN ISO 9227:2023-02 + A1:2024-10

Title (PL)

Badania korozyjne w sztucznych atmosferach — Badania w rozpylonej solance

Title (EN)

Corrosion tests in artificial atmospheres — Salt spray tests

Step-by-step procedure

1. Solution

   Dissolve sodium chloride in water with a conductivity ≤ 20 µS/cm to 45–55 g/l; for AASS add acetic acid, for CASS also copper(II) chloride (0,26 ± 0,02) g/l; filter if necessary (5.1–5.3).

2. pH

   Set the pH on the basis of the solution collected in the cabinet: NSS 6,5–7,2, AASS and CASS 3,1–3,3 at (25 ± 2) °C; electrometric measurement with electrodes for weakly buffered solutions.

3. Cabinet and collecting devices

   Check the distribution of the fall-out with collecting devices (at least six when checking the cabinet, two during the test); after AASS or CASS, clean the cabinet thoroughly and check the pH of the collected solution before NSS (6.5–6.6).

4. Specimens

   Prepare and arrange the specimens according to the product specification and Clauses 8–9 of the standard; in the 1990 edition — flat specimens with the test surface upwards, as close as possible to 20° from the vertical (15–30°), without solution dripping onto specimens below.

5. Exposure

   Run the test at the temperature and fall-out of Clause 10 of the standard for the period from the product specification; check the fall-out and the concentration of the collected solution.

6. Evaluation

   After the test, treat the specimens according to Clause 12 and evaluate them according to the product specification; prepare the test report according to Clause 14.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Hydrochloric acid (CAS 7647-01-0) — toxic, corrosive, irritating, very toxic to aquatic life; handled by skilled personnel or under their control, with care in disposal (warning in 5.2.2)
• Sodium hydroxide (CAS 1310-73-2) — toxic, corrosive, irritating; handling as above (5.2.2)
• Glacial acetic acid (CAS 64-19-7) — flammable liquid, toxic, corrosive, irritating; handling as above (5.2.3)
• Copper(II) chloride dihydrate (CAS 10125-13-0) — toxic, corrosive, irritating, very toxic to aquatic life; handling as above (5.2.4)
• The standard gives preference to apparatus that can treat the fog before releasing it from the building and dilute the solution before discharging it to the drainage system (6.2)

Frequently asked questions