Salt Spray Testing Lab

What is Salt Spray Testing ?

Salt spray testing is an accelerated corrosion test that is done on a sample by exposing it to a salt solution of known or defined composition.

During Salt Spray testing, a corrosive attack is generated on a representative sample like coated metal strips in order to evaluate (mostly comparatively) the suitability of the coating for use as a protective finish.

The appearance of corrosion products (rust or other oxides) is evaluated after a defined period of time. Test duration depends on the corrosion resistance of the coating; generally, the more corrosion resistant the coating is, the longer the period of testing before the appearance of corrosion or rust.

Salt spray tests are conducted in a closed testing chamber. A salt water solution is applied to a sample via a spray nozzle. This dense salt water fog is used to imitate a corrosive experiment. 

Salt spray testing Lab

ISO 9227: 2017 Corrosion tests in artificial atmospheres – Salt spray tests

This ISO standard takes precedence over many methods as this is the most used standard. This method may need to be changed to conform to the standard.

Continuous exposure to salt spray at 35 ° C +/- 2 ° C with a salt concentration of 5% NaCl +/- 1%.

Three variants exist within the standard:

  • NSS: Neutral Salt Spray (mixture of demineralized water and pure salt) after allowing the solution to stabilize for several hours, the salinity and the pH are measured and recorded. Any pH adjustment can be made using reagent grade hydrochloric acid (HCL) to increase acidity or regent grade sodium hydroxide (NaOH) or sodium bicarbonate (NA2CO3) to reduce acidity. acidity.
  • AASS: Acetic Salt Spray (NSS solution + glacial acetic acid) glacial acetic acid is added to the neutral saline solution so that the pH meets the required limits stipulated in the standard. Any pH adjustment can be made using glacial acetic acid to increase acidity or regent grade sodium hydroxide (NaOH) or sodium bicarbonate (NA2CO3) to reduce acidity. Record all results.
  • CASS: Cupro Acetic Salt Spray (NSS solution + copper chloride dihydrate) at 50 ° C +/- 2 ° C. Copper chloride dihydrate (CuCl2 2H2O) is added to the neutral saline solution to give a concentration of 0.26 g / L (+/- 0.01 g / L) Any adjustment of the pH must be carried out using glacial acetic acid to increase acidity or regent grade sodium hydroxide (NaOH) or reactive grade sodium bicarbonate (NA2CO3) to reduce acidity. Save all results.

The neutral salt spray (NSS) test particularly applies to

– metals and their alloys,
– metallic coatings (anodic and cathodic),
– conversion coatings,
– anodic oxide coatings, and
– organic coatings on metallic materials

The acetic acid salt spray (AASS) test is useful for testing decorative coatings of copper + nickel + chromium, or nickel + chromium. This method is very suitable for testing coating effectiveness ( anodic and organic) on aluminium.

The copper-accelerated acetic acid salt spray (CASS) test is useful for testing various decorative coatings

CASS testing

ISO 16151:2018

Accelerated cyclic test with exposure to acidified salt spray, dry and wet conditions

ISO 16151specifies two accelerated corrosion-test methods. Methods A and B, for the comparative evaluation of metallic materials with or without permanent corrosion protection or temporary corrosion protection in outdoor salt and/or acid rain environments.

The particular advantages of the two tests over conventional accelerated tests, such as the neutral salt spray (NSS) test as specified in ISO 9227 lie in their better ability to reproduce the corrosion that occurs in outdoor salt and/or acid rain environments.

ISO 11474:1998

Corrosion tests in artificial atmosphere — Accelerated outdoor test by intermittent spraying of a salt solution (Scab test)

The accelerated outdoor corrosion test applies to

  • — organic coatings on metals;
  • — metallic coatings (anodic and cathodic);
  • — chemical conversion coatings;
  • — metals and their alloys.

In this method, the corrosion process during outdoor exposure is accelerated by intermittently spraying a solution of sodium chloride (mass fraction 3 %) on to the test surface thus simulating and enhancing the environmental stress prevailing at marine test sites.

ISO 11997-3:2022

Determination of resistance to cyclic corrosion conditions-Testing of coating systems on materials and components in automotive construction

This salt spray testing method uses corrosive conditions (temperature and humidity ramps and salt spray) to create artificial corrosion patterns.

These corrosion patterns are very common to be faced for automobiles, and they are equivalent to similar protective coating systems. This salt spray accelerated test investigates the delamination/corrosion creep that results from defined artificial damage to a coating.

Investigations of surface and edge corrosion or investigations of adhesive specimens or components are also covered. This cyclic corrosion test is also suitable for testing corrosion in flanged areas or near gaps.

This salt spray testing standard was developed for the assessment of coated substrates (test specimens, bodywork and mounted parts) in the automotive industry particularly for coating systems on aluminium, steel or galvanized steel but it can also be used for the assessment of the corrosion resistance of coating systems on other metals and their alloys.

ISO 21746:2019

The potential benefits to CFRP-metal users of implementing a galvanic corrosion test based on this document are:

a) addressing corrosion risks relating CFRPs of drastically nobler galvanic potential than metals to form a global cell between CFRP and metal –

b) expanding CFRP applications to the fields of corrosive environments that still require the combinations with metallic components;

c) the detection or the prevention of galvanic current insulation loss, such as ion migration and time-related degradation in sealant film, injected calking layer and glass fibre reinforced plastics (GFRPs) layer;

d) demonstrating the conformity to specified conditions for type certification requirements in the engineering such as aircraft developments;

e) evaluating the corrosion related procedures for maintenance, repair and overhaul (MRO) in the engineering operations such of CFRP aircrafts.

ISO 16701:2015

Accelerated corrosion test involving exposure under controlled conditions of humidity cycling and intermittent spraying of a salt solution

This standard specifies the salt spray test method, to be used in an accelerated atmospheric corrosion test constituting of 6 hours exposure to a slightly acidified solution of 1 % NaCl twice weekly, followed by a condition of controlled humidity cycling between 95 % RH and 50 % RH at a constant temperature of 35 °C.

The accelerated laboratory corrosion test with salt spray applies to

  • — metals and their alloys,
  • — metallic coatings (anodic or cathodic),
  • — chemical conversion coatings, and
  • — organic coatings on metallic materials.

ISO 14993:2018

Corrosion of metals and alloys — Accelerated testing involving cyclic exposure to salt mist, dry and wet conditions

The test involves cyclic exposure of the specimens to neutral salt mist, “dry” and “wet” conditions.

The particular advantages of this test over common accelerated tests such as the neutral salt spray (NSS) test lie in its ability to better reproduce the corrosion that occurs in outdoor salt-contaminated environments

ISO 21207:2015

Corrosion of metals and alloys — Accelerated testing involving cyclic exposure to salt mist, dry and wet conditions

This standard defines two accelerated corrosion test methods to be used in assessing the corrosion resistance of products with metals in environments where there is a significant influence of chloride ions, mainly as sodium chloride from a marine source or by winter road de-icing salt, and of corrosion-promoting gases from industrial or traffic air pollution

Test method A involves exposure of the test objects to the following test cycle:

  • a) neutral salt spray testing (ISO 9227) for 2 h in a mist of a sodium chloride salt solution of mass fraction 5 % at 35 °C, followed by drying for 22 h in a standard laboratory climate;
  • b) exposure for 120 h in a test atmosphere containing a mixture of corrosion-promoting gases, volume fraction of NO2 equal to 1,5 × 10−6 and of SO2 equal to 0,5 × 10−6, at a relative humidity of 95 % and at a temperature of 25 °C, followed by drying for 24 h in a standard laboratory climate.

Test method B involves exposure of the test objects to the following test cycle:

  • a) neutral salt spray testing (ISO 9227) for 2 h in a mist of a sodium chloride salt solution of mass fraction 5 % at 35 °C, followed by drying for 22 h in a standard laboratory climate;
  • b) exposure for 48 h in a test atmosphere containing a mixture of corrosion-promoting gases, volume fraction of NO2 equal to 10 × 10−6 and of SO2 equal to 5 × 10−6, at a relative humidity of 95 % and at a temperature of 25 °C;
  • c) neutral salt spray testing (ISO 9227) for 2 h in a mist of a sodium chloride salt solution of mass fraction 5 % at 35 °C, followed by drying for 22 h in a standard laboratory climate;
  • d) exposure for 72 h in a test atmosphere containing a mixture of corrosion-promoting gases, volume fraction of NO2 equal to 10 × 10−6 and of SO2 equal to 5 × 10−6, at a relative humidity of 95 % and at a temperature of 25 °C.

ASTM G85-19

This standard sets forth conditions for five modifications in salt spray (fog) testing for specification purposes. These are in chronological order of their development:

1) Annex A1,  acetic acid-salt spray test, continuous.

2) Annex A2,  cyclic acidified salt spray test.

3) Annex A3,  seawater acidified test, cyclic (SWAAT).

4) Annex A4,  SO2 salt spray test, cyclic.

5) Annex A5,  dilute electrolyte cyclic fog dry test.

ASTM D2059/D2059M-03(2022)

This standard covers the determination of the resistance of all types of zippers to corrosion and their ability to function properly after exposure of specified duration in a prescribed salt spray.

ASTM B368-21 (CASS TEST)

Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog)

This test method prescribes the conditions required in copper-accelerated acetic acid-salt spray (CASS) testing for specification purposes.  This test method is applicable to evaluating the corrosive performance of decorative copper/nickel/chromium or nickel/chromium coatings on steel, zinc alloys, aluminum alloys, and plastics designed for severe service. It is also applicable to the testing of anodized aluminum. 

UV /water condensation weathering

  • ISO 11507                        
  • IEC 61345
  • EN 13523-10
  • ASTM D4587

Moist SO2 (Kesternich) tests

  • EN ISO 3231            
  • ISO 6988
  • ASTM G 87
  • ASTM G 85, Practice A4
  • DIN 50 018

Other standards for Salt spray tests

  • NFX 41-002
  • JIS Z 2371
  • IEC 60068-2-11
  • MIL-STD-810, Test Method 509.5
  • MIL-DTL-5541F