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Contributors to waterside corrosion of soil-steel structures

University of British Columbia

Soil-steel structures are designed and constructed worldwide for use in civil infrastructure and construction industries. As a result, extensive work has been devoted to understanding the corrosion of zinc and galvanized steel yielding the development of various corrosion models worldwide. Canada does not have a corrosion model required for use in design, but engineers and contractors often use that developed in the United States by the American Association of State Highway and Transportation Officials. This corrosion model defines the recommended range of pH, chloride concentration and soluble sulphate concentration as well as minimum resistivity for unsaturated soil applications. However, these design recommendations and associated corrosion model are often misused in aqueous environments. As a result, many structures have demonstrated significant evidence of premature corrosion raising concerns with the suitability of this corrosion model. Field testing was conducted on both mechanically stabilized earth retaining walls as well as corrugated steel pipe. Steel samples were extracted for analyses with scanning electron microscope and energy dispersive x-ray spectroscopy while water samples were collected to determine the properties causing degradation. Linear polarization resistance was also completed on two mechanically stabilized earth walls to obtain in-situ corrosion rates. To complement field work, laboratory experiments were conducted on galvanized steel samples in electrolytes simulating environments satisfying design criteria recommending by the American Association of State Highways and Transportation Officials as well as outside the scope of this model. Relative corrosion rates were calculated from results obtained from accelerated corrosion testing and sample surfaces were analyzed with the use of a scanning electron microscope. Through laboratory experimentation and field testing it has been discovered that the hardness of water affects the formation of the outermost protective layer on zinc articles, the zinc patina. The following dissertation challenges the appropriateness of durability design criteria and associated corrosion model, defined by the American Association of State Highway and Transportation Officials, for use in aqueous environments while offering guidance on the development of more suitable guidelines for conditions other than unsaturated soil.

Text

2013-12-11

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/45606

Materials Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/