American Society of Civil Engineers

H2S Entrapment and Corrosion on Direct Embedded Galvanized Steel Transmission Poles

by Ajay Mallik, P.E., A.M.ASCE, (President, SANPEC, Inc, 11819 Skydale Drive, Tomball, TX 77375 E-mail: and Andy Cooper, (Safety Manager, LCRA Transmission Services Corporation, 3505 Montopolis Drive, Austin, Texas, 78744 E-mail:

pp. 1-11, (doi:

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Document type: Conference Proceeding Paper
Part of: Electrical Transmission and Substation Structures 2009: Technology for the Next Generation
Abstract: Hydrogen sulfide (H2S) is a colorless, toxic, and flammable gas with a characteristic odor of rotten eggs. It occurs naturally in crude petroleum, natural gas, volcanic gases, and hot springs. It can also result from bacterial breakdown of sulfates in organic matter, such as in swamps and sewers. H2S gas forms sulfuric acid when concentrations exceed approximately 2.0 ppm and causes corrosion on many underground construction materials and is particularly devastating to concrete and steel. Temperature can accelerate chemical corrosion due to creation of sulfuric acid. Warmer climates -southern US cities, for example - have more corrosion problems. It can also lead to sulfide stress cracking. This paper addresses the corrosion issues due to H2S gas on some galvanized steel transmission poles and the precautions taken related to the removal and replacement of the direct embedded steel poles with base plated steel poles on a traditional concrete pier foundation. This was a dangerous situation, but also an interesting exercise in developing a solution to the abatement of the toxic and corrosive gas, as well as evaluation and removal of the pole itself. Special techniques that were necessary in dealing with the toxic gas that may prove beneficial to others who may come across similar situations.

ASCE Subject Headings:
Electric transmission structures