What is Neutral Salt Spray Testing?
Neutral salt spray testing is a standardised test method which is used to qualify and comparatively quantify the corrosion resistance of coated components and other specimens.
For example, when an aluminium component is coated with anodising, this provides not only an attractive cosmetic finish to the component, more importantly it provides high corrosion resistance. The coating is intended to provide the component with high corrosion resistance through the life of the part, however it is necessary to verify the corrosion resistance of the coating to make these claims.
Neutral salt spray (NSS) testing is an accelerated corrosion test, which is used to predict the suitability of a protective coating. This is achieved by exposing test panels or components in a chamber, where they are continuously exposed to sodium chloride (salt) mist at an elevated temperature for a set period of time. After the required period, the panels/components are examined by our technicians who will look for signs of corrosion and any other visible, superficial defects.
Salt spray testing is also sometimes referred to as salt mist testing or salt fog testing.
Neutral salt spray testing will typically run from 24 to 500 hours, however we can work outside of this range if required by our customers. We will provide a test report as standard to salt spray testing customers and for an additional cost we can provide periodic photographs and/or consultancy.
Our records include and our reports can optionally include the following data:
- Type of salt and water used in preparing the salt solution.
- Exposure variables at each monitoring point, such as chamber temperature, condensate volume, condensate pH and condensate salt concentration/S.G.
- Type of specimen and its dimensions, or number or description of part.
- Method of cleaning specimens before and after testing.
- Method of supporting or suspending article in the salt spray chamber.
- Description of masking/protection used (if any).
- Exposure period - usually a multiple of 24, such as 168 hours or 336 hours.
- Interruptions in exposure, cause, and length of time.
- Results of all inspections.
Typical Coatings Tested
- Anodising on aluminium.
- Electroplated metals: e.g. zinc, chromium, nickel, copper and tin.
- Non-electrolytic conversion coatings: , e.g. Alocrom, phosphating, etc
- Painted surfaces
- Stainless steel surfaces – with or without treated surfaces
- ASTM B117
- MIL-A-8625 (refers to ASTM B117)
We are accredited to Nadcap AC7108, our neutral salt spray testing is included in this specification.
Information That We Require
Salt spray testing is only useful when comparing like for like, this requires control of various factors. You will need to supply us with the following information (although we may be able to suggest sensible defaults):
- Exposure angle (6° is common on aluminium substrates, 15° is the default in ASTM B117 and common on steel substrates)
- Exposure duration (often between 24 and 500 hours)
- Cleaning requirements before exposure
- Examination requirements
All this information is required at the quoting stage for an accurate quote, although we should be able to provide a budget quote without.