text: ASTM G85 is the most popular global test standard covering modified salt spray tests. There are five such tests altogether, referred to in ASTM G85 as annexes A1 through to A5. Many of these modified tests originally arose within particular industry sector, in order to address the need for a corrosion test capable of replicating the effects of naturally occurring corrosion and accelerate these effects.
  This acceleration arises through the use of chemically altered salt spray solutions, often combined with other test climates and in most cases, the relatively rapid cycling of these test climates over time. Although popular in certain industries, modified salt spray testing has in many cases been superseded by cyclic corrosion testing (CCT) 
  The type of environmental test chambers used for modified salt spray testing to ASTM G85 are generally similar to the chambers used for testing to ASTM B117, but will often have some additional features, such as an automatic climate cycling control system.
  ASTM G85 Annex A1 – Acetic Acid Salt Spray Test (non-cyclic) 
  This test can be used to determine the relative resistance to corrosion of decorative chromium plating on steel and zinc based die casting when exposed to an acetic acid salt spray climate at an elevated temperature. This test is also referred to as an ASS test.
  Test specimens are placed in an enclosed chamber and exposed to a continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard and acidified (pH 3.1–3.3) by the addition of acetic acid. This spray is set to fall-out on to the specimens at a rate of 1–2 ml/80 cm/hour, in a chamber temperature of 35 °C. This climate is maintained under constant steady state conditions. The test duration is variable.
  ASTM G85 Annex A2 – Acidified Salt Fog Test (cyclic).
  This test can be used to test the relative resistance to corrosion of aluminium alloys when exposed to a changing climate of acetic acid salt spray, followed by air drying, followed by high humidity, all at an elevated temperature. This test is also referred to as a MASTMAASIS test.
  Test specimens are placed in an enclosed chamber, and exposed to a changing climate that comprises the following 3 part repeating cycle. 0.75 hours exposure to a continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard and acidified (pH 2.8–3.0) by the addition of acetic acid. This spray is set to fall-out on to the specimens at a rate of 1–2 ml/80 cm/hour. This is followed by a 2 hour exposure to an air drying (purge) climate. This is followed by 3.25 hours exposure to a high humidity climate which gradually rises to between 65% RH and 95% RH. The entire test cycle is at a constant chamber temperature of 49 °C. The number of cycle repeats and therefore the test duration is variable.
  ASTM G85 Annex A3 – Seawater Acidified Test (cyclic)
  This test can be used to test the relative resistance to corrosion of coated or uncoated aluminium alloys and other metals, when exposed to a changing climate of acidified synthetic seawater spray, followed by a high humidity, both at an elevated temperature. This test is also referred to as a SWAAT test.
  Test specimens are placed in an enclosed chamber, and exposed to a changing climate that comprises the following 2 part repeating cycle. First, a 30 minute exposure to a continuous indirect spray of synthetic seawater solution, prepared in accordance with the requirements of the test standard and acidified (pH 2.8–3.0) by the addition of acetic acid. This spray is set to fall-out on to the specimens at a rate of 1–2 ml/80 cm/hour. This is followed by a 90 minute exposure to a high humidity climate (above 98% RH). The entire test cycle is at a constant chamber temperature of 49 °C (may be reduced to 24–35 °C for organically coated specimens). The number of cycle repeats and therefore the test duration is variable.
  ASTM G85 Annex A4 –  Salt Spray Test (cyclic)
  This test can be used to test the relative resistance to corrosion of product samples that are likely to encounter a combined /salt spray/acid rain environment during their usual service life.
  Test specimens are placed in an enclosed chamber, and exposed to 1 of 2 possible changing climate cycles. In either case, the exposure to salt spray may be salt water spray or synthetic sea water prepared in accordance with the requirements of the test standard. The most appropriate test cycle and spray solutions are to be agreed between parties.
  The first climate cycle comprises a continuous indirect spray of neutral (pH 6.5–7.2) salt water/synthetic seawater solution, which falls-out on to the specimens at a rate of 1–2 ml/80 cm/hour. During this spraying, the chamber is dosed with  gas at a rate of 35 cm/minute/m of chamber volume, for 1 hour in every 6 hours of spraying. The entire test cycle is at a constant chamber temperature of 35 °C. The number of cycle repeats and therefore the test duration is variable.
  The second climate cycle comprises 0.5 hours of continuous indirect spray of neutral (pH 6.5–7.2) salt water/synthetic seawater solution, which falls-out on to the specimens at a rate of 1–2 ml/80 cm/hour. This is followed by 0.5 hours of dosing with  gas at a rate of 35 cm/minute/m of chamber volume. This is followed by 2 hours of high humidity soak. The entire test cycle is at a constant chamber temperature of 35 °C. The number of cycle repeats and therefore the test duration is variable.
  ASTM G85 Annex A5 – Dilute Electrolyte Salt Fog/Dry Test (cyclic)
  This test can be used to test the relative resistance to corrosion of paints on steel when exposed to a changing climate of dilute salt spray at ambient temperature, followed by air drying at elevated temperature.
  It is a popular test in the surface coatings industry, where it is also referred to as the PROHESION test.
  Test specimens are placed in an enclosed chamber, and exposed to a changing climate with the following 2-part cycle.
  First, a 1-hour exposure to a continuous indirect spray of salt water solution, prepared in accordance with the requirements of the test standard and acidified (pH 3.1–3.3) by the addition of acetic acid.
  This spray is set to fall on the specimens at a rate of 1–2 ml/80 cm/hour, in an ambient chamber temperature (21–27 °C). This is followed by a 1-hour exposure to an air drying (purge) climate at 35 °C.
  The cycle repeats until the desired duration has been achieved.