What Does Streicher Test Mean?
The Streicher test is a corrosion detection method for intergranular attack. This method is based on weight loss determinations and provides a quantitative measure of the relative performance of the material being evaluated. This test is also designed to detect grain boundary segregation and sensitization, but with a much shorter test duration.
This test was developed by and named after Michael A. Streicher, an American metallurgist and a leading developer of corrosion tests for stainless steels and other corrosion-resistant alloys.
The Streicher test is also known as the ASTM A262 method B test.
Corrosionpedia Explains Streicher Test
The Streicher test was developed specifically for intergranular corrosion detection in austenitic stainless steel. The procedure includes subjecting a specimen to a 24- to 120-hour boil in ferric sulfate (50% sulfuric acid). This procedure measures the susceptibility of stainless steels and nickel alloys to intergranular attack associated with the precipitation of chromium carbides at grain boundaries.
This test is faster than the Strauss test because of increased acid concentration. Furthermore, the oxidizer in this test is Fe3+, which is stronger than Cu2+. The Streicher test uses weight loss to measure the attack rather than macroscopic evaluation. In this regard, it is more quantitative than the Strauss test.
Streicher testing is carried out on samples from finished tubes in the as-delivered condition or on material that has been sensitized (heated in the critical temperature range in a furnace or by welding).
Unlike the Huey test, the Streicher test is relatively insensitive to molybdenum variations and was developed only to determine the degree of intergranular sensitization. Thus, the Streicher test must not be used to compare alloys for service because it does not predict service life. To properly evaluate an alloy in this test, it is necessary to know a benchmark rate that the alloy should reach. An alloy is considered acceptable if the corrosion rate is less than its benchmark.
Besides the final heat treatment, there are several factors that influence the corrosion rate of an alloy in the Streicher test. The chemical composition is the largest influence on the corrosion rate of an alloy. Changes in chromium, carbon, molybdenum, tungsten, and iron also influence the corrosion rate. Alloys with higher chromium generally exhibit lower corrosion rates.