SEDL / STP / STP576-EB / STP41407S

Interpretation of Pitting Corrosion Data from Statistical Prediction Interval Calculations

Crews, D. L.
Research consultant, Clow Corporation, Coshocton, Ohio

Pages: 14    Published: Jan 1976

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Abstract

The National Bureau of Standards data for pitting corrosion of ductile iron and steel pipe in four soils and gray cast iron and 3-in. Bessemer steel pipe in one soil have been treated by statistical methods to obtain the prediction intervals of estimated pit depths as a function of time. In the nonaggressive soils which are representative of most pipe installations, these ductile iron and gray iron pipe exhibited less corrosion than the companion steel pipe.

Prediction interval calculations are useful for quantitative analysis of corrosion data which has considerable inherent scatter and where service life is determined by the failure at relatively few points.