Fog Testing

Definition - What does Fog Testing mean?

Fog testing is a standardized accelerated corrosion test used to evaluate the relative corrosion resistance of materials exposed to a salt spray or salt fog at an elevated temperature. Aside from corrosion resistance, fog testing is an excellent way to test the permeability of coatings and seals.

Fog testing is used in:

  • Industrial sector
  • Construction
  • Marine
  • Automotive
  • Military
  • Aircraft and aerospace

Fog testing is also known as ASTM B117, salt fog test, salt spray test, neutral salt spray (NSS) and spray fogging.

Corrosionpedia explains Fog Testing

In fog testing, test specimens are positioned in an enclosed salt spray testing cabinet or chamber and subjected to a continuous indirect fog or spray of a saltwater solution. This climate is maintained throughout the duration of the test.

Fog testing is used to:

  • Compare the corrosive resistance of various metals or finishes
  • Determine the corrosive tendency when a metal or coated surface is scratched
  • Measure coating adhesion and corrosion creep
  • Estimate corrosion resistance in a marine environment

Fog testing, or ASTM B117 Salt Spray Test standard (and ISO 9227), are widely used reference standards to determine normal corrosion resistance to ocean water-type environments.

The following coatings can be evaluated by this test:

  • Phosphated surfaces
  • Painted metal surfaces
  • Organic coatings
  • Zinc/zinc-alloy electroplating
  • Electroplated chromium, nickel, copper, tin
  • Coatings not applied electrolytically
  • Painted surfaces with an underlying hot-dip galvanized coating
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