Salt spray testing is a common accelerated corrosion test method that exposed metallic and non-metallic materials to a highly corrosive environment, over an extended period of time, in order to assess their relative corrosion resistance. The testing can also be used to determine the effectiveness of paints and coatings at protecting the substrate material from corrosion.

Salt spray testing is usually carried out to most widely used standard ASTM B117 neutral salt spray test for between 24 and 1000 hours, however this may be specified. The testing typically involves using a 5% sodium chloride (NaCl) solution with is atomised within a sealed chamber to create a saltwater mist, accelerating the corrosion of the materials being tested.

The test samples are generally inspected at regular intervals to monitor and record the degradation of the samples until either the client wants to terminate the test such as when corrosion has initiated or after the specified time has elapsed.

MERI is equipped with an Ascott Analytical CC450iP 450 litre salt spray cabinet with is capable of allowing a bespoke program to be established such as introducing cyclic wet/dry testing as well as modify the humidity and temperature allowing a range of standards to be utilised, such as ASTM G85, ISO 7253 and DEF STAN 1053 method 36.

Upon completion of the testing analysis of the samples using the Infinite Focus Microscope may allow for localised corrosion events such as pitting in metallic materials to be characterised allowing the depth of penetration to be determined, helping to determine the severity of corrosion.

SEM and EDX analysis may also indicate for example whether any corrosion inhibitors present in paints and coatings are working as well as allowing high magnification high resolution imaging and elemental analysis. 

Should further quantification of the corrosion products be required, X-Ray Diffraction may be performed to determine what corrosion compound has formed.

Analysis of the failure of the paints and coatings applied to the substrate material, such as through the formation of blisters due to holidays in the paints may indicate ways in which to improve the formulation.

Salt spray testing may be performed in parallel with other electrochemical techniques, such as electrochemical impedance spectroscopy and potentiodynamic polarisation, to improve the understanding of the material system regarding corrosion performance.

External Links

• Some background to salt spray testing can be found on the Corrosion Doctors website.
• The ASTM Standard relating to neutral salt spray testing is B117
• Equipment manufacturer - Ascott Analytical

For further information, please contact +44(0)114 225 3500 or MERI@shu.ac.uk.