Abstract
The thickness reduction due corrosion of weathering steels can be estimated by using alloy index V and local corrosive environment index Z. However, it is required to calculate Z that costly measurement of air borne salt, sulfur oxides and so on. Thus, atmospheric corrosion monitor sensor (ACM sensor) was examined as an alternative way of environmental corrosivity measurement. At first, characteristics of ACM sensor output were checked by laboratory test. Then, the measurements of environmental corrosivity with ACM sensor were conducted at exposure test sites under un-sheltered condition. ACM sensor output and corrosion behavior of weathering steels were compared to identify adequate index of ACM sensor output. As a result, followings were obtained: (1) ACM sensor's output current was not affected by temperature. Thus, temperature must be considered as an additional factor. (2) Annual electric charge QACM was suited as an index of ACM sensor output because log (QACM) was proportional to corrosion rate parameter Bs of Y = AsXBs . (3) The estimation equation of thickness reduction due corrosion was statistically obtained as Y = (166 + 8.71/V - 0.276QACM - 0.480T) X(0.326/V + 0.0918 log(QACM - 0.0165T) - 0.154[Cr]) , where Y is thickness reduction due corrosion [μm], X is exposed period [year], T is annual averaged temperature [K] and [Cr] is mass percent of chromium in the steel. It might be said from the findings in this study that thickness reduction due corrosion of new weathering steels can be estimated more accurately by combination of one year exposure test of small samples for As and ACM sensor measurement for Bs.
