Assessment of hydrogen sulfide corrosion of cementitious sewer pipes: a case study

A study was conducted to assess hydrogen sulphide corrosion in cementitious sewer pipes and concrete culverts existing in the four largest coastal cities and their environs in Lebanon. Significant factors and parameters affecting H2S corrosion were measured both in the field and in the laboratory. All collected samples were obtained from existing sewer networks that are more than 30 years old. Pipe samples obtained from these locations did not exhibit any corrosion indicators. Alkalinity measurements indicated the occurrence of mild corrosion leading to neutralization of concrete (calcareous aggregates) particularly at the pipe crown. Testing for the sulphate content of the samples did not reveal a clear trend as to the distribution of sulphates along the pipe circumference. Parameters of the existing sewer networks upstream of sample sites, along with survey data obtained from the field were introduced into commercial software for the evaluation of sulphide generation and annual corrosion rates. The results indicated that hydrogen sulphide will only be generated in negligible quantities under the prevailing environmental conditions, and hence H2S corrosion could proceed, but at very slow rates