ASTM G85 Annex 4 Cyclic SO2 Testing
Assured Testing Services performs Standard Practice for Modified Salt Spray Testing per ASTM G85 Annex A4, also known as Cyclic SO2 Salt Spray. The ASTM G85 Annex A4 Cyclic SO2 Salt Spray standard only prescribes the equipment, the procedure, the electrolyte solution, and the conditions needed to maintain the modified acidified salt fog test environment. The conditions inside a chamber operating ASTM G85 Annex A4 Cyclic SO2 Salt Spray exposure are 35C or temperature, with continuous electrolyte spray/fog at a humidity >98% RH using an electrolyte consisting of 5% pure sodium chloride to which SO2 gas is injected at a rate up to 35 cm 3 / m 3 -min. This results in the pH of the collected fog condensate of 2.5 - 3.2. The electrolyte is controlled such that its rate of condensation on the specimens is at a rate of 1.0 to 2.0 ml /80 cm² / hour. ASTM G85 Annex A4 Cyclic SO2 Salt Spray exposure is conducted in a six (6) hour cycle, with SO2 injection taking place during the last hour of the cycle.
The ASTM G85 Annex A4 Cyclic SO2 Salt Spray standard references other ASTM standards which Assured Testing Services maintains on its ISO 17025 scope. The other reference documents in ASTM G85 are listed here:
ASTM B117 “Practice for Operating Salt Spray (Fog) Apparatus”
ASTM D609 “Practice for Preparation if Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings,
and Related Coating Products”
ASTM D1141 “Practice for the Preparation of Substitute Ocean Water”
ASTM D1193 “Specification for Reagent Water”
ASTM D1654 “Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments”
ASTM E70 “Test Method for pH of Aqueous Solutions With the Glass Electrode”
The purpose of the ASTM G85 Annex A4 Cyclic SO2 Salt Spray test is to provide a controlled accelerated corrosive environment to evaluate the relative corrosion resistance of typically chromated aluminum articles, aluminum heat exchangers, and ferrous components finished with
either organic or inorganic coatings.
Assured Testing Services has multiple chambers available to expose samples of various dimensions for the ASTM G85 Annex A4 Cyclic SO2 Salt Spray test. The number of test
specimens, dimensions, and duration of exposure for the test can be specified by the customer, or found on a part drawing detail block, or in a governing specification.
When exposing parts in accordance with ASTM G85 Annex A4 Cyclic SO2 Salt Spray test, samples are submitted in replicates for validation and comparison purposes. While the specimens are in the exposure chamber, they are usually positioned in the intended in-service orientation of the coponent, or in the case of panels, at an angle from 15 to 30 degrees from vertical. The duration of the test varies depending on the requirements of the specimens.
The most recent version of ASTM G85 Annex A4 Cyclic SO2 Salt Spray can be obtained from