The cut edge of the specimen should be finely ground, and then cleaned and passivated in sulfuric acid with a volume concentration of 20% to 30% and a temperature of 60 to 66 ℃ for half an hour. The sample of 316 and 317 rubber joint is not corroded or corroded very slowly (no bubbles), and the experiment does not change color within 10~15 minutes. If you choose to test together with a known composition of the test to make a close comparison, the experiment can be more accurate.

