Precision Analysis of Rotary Hanging Piece Method for Measuring Corrosion Inhibition Performance of Water Treatment Agent

In order to estimate the precision of rotary hanging piece method for determining the corrosion inhibition performance of water treatment agent on 20# carbon steel in seawater,the data from precision common tests were statistically analyzed using the graph and numerical methods.The consistency and outliers of 92 data from five laboratories were investigated.The results indicated that there were only 3 stragglers but no statistical outlier was detected,which showed that 92 data were valid.The method precision can be expressed as follows: the repeatability standard deviation and the repeatability limit were 0.005 1 and 0.037 respectively,and the reproducibility standard deviation and the reproducibility limit were 0.078 7 and 0.045 respectively when testing corrosion rate between was 0.456 mm/a and 0.490 mm/a.There is no statistically significant correlations between the method precision and the oven mean.It is proved by using the rotary hanging piece method that Biocide SW303 had corrosion inhibition performance on 20# carbon steel in seawater.The linear correlation coefficient was 0.966 9 between the corrosion inhibition rate of carbon steel and SW303 concentration (p＜0.01).