Abstract: The influence of detrimental intermetallic phase in duplex steels on their toughness and corrosion resistance can be detected by the ASTM A923-2014 standard ferric chloride corrosion test method, with the value characterized by corrosion rate. This paper analyzes the uncertainties due to the weight, length, width and thickness of the samples before and after the corrosion. The uncertainty components were calculated and then combined to obtain the expanded uncertainty. Taking into account the expanded uncertainty and other factors, the upper limit of the acceptance criteria for the test method was chosen. In order to eliminate the detrimental intermetallic phase and finally improve the product quality, proper heat treatment is needed on the samples exceeding the upper limit. The results showed that the detrimental intermetallic phase of 2205 duplex stainless steel was (3.9±1.4) mg/(dm²·d), with a coverage factor k=2. The upper limit of the acceptance criteria for this test method was chosen to be 8 mg/(dm²·d).