SEDL / STP / STP1222-EB / STP12673S

The Effects of Sulfuric Acid on Calcium Carbonate Filled PVC Sewer Pipe Compounds

Hawkins, TW
Director of Material Engineering, The Lamson & Sessions Co., Cleveland, OH

Mass, TR
Senior Plastics Engineer, The Lamson & Sessions Co., Cleveland, OH

Pages: 13    Published: Jan 1994

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Abstract

Even though calcium carbonate filled rigid polyvinyl chloride (UPVC) sanitary sewer pipe has been used since 1973, concerns are occasionally raised regarding its possible corrosion by sulfuric acid present in the sewer gas environment. In this study two calcium carbonate filled PVC pipe compounds, under prestressed conditions, are exposed to sulfuric acid (20%) for extended periods. The effects of the sulfuric acid on the calcium carbonate in the compounds are qualitatively measured by scanning electron microscopy (SEM) and quantitatively determined by wavelength dispersive x-ray microanalysis (WDS). The study shows that only the calcium carbonate immediately at the surface is affected by the sulfuric acid. The calcium carbonate below the surface is well dispersed and completely encapsulated in a continuum of PVC with no inner-connectivity between neighboring calcium carbonate particles and is unaffected. Results for samples exposed for 14 days, 30 days, 90 days and 6 months are included.