Page 149 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

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CORROSION CAUSES

3.1 INTRODUCTION

The general causes of corrosion of material objects vary with the nature of the atmo-
sphere to which the metallic object or component is exposed. The corrosives can be
mineral acids, such as hydrochloric, sulfuric or carbonic acid, or gases such as carbon
dioxide, sulfur dioxide, or hydrogen sulfide. In certain cases, it is possible that one
might encounter hydrogen fluoride. Anions such as chloride and sulfite can be quite
deleterious.

3.2 CORROSION IN CONVENTIONAL CONCRETE BRIDGES

The main cause of reinforced concrete bridge deterioration is chloride-induced
corrosion of the black steel reinforcement, resulting in expansion forces in the
concrete that produce cracking and spalling of the concrete. The source of chloride
can be from either marine exposure or the deicing salts used in snow and ice removal.
The use of deicing salts is likely to continue, if not increase. Very little can be done
to prevent bridge structures from getting exposed to corrosive chloride salts.

3.3 CORROSION OF PRESTRESSED CONCRETE BRIDGES
Most of these bridges are relatively new, and the overall economic impact is not as
significant as for conventional reinforced concrete bridges. It is estimated that the

Challenges in Corrosion: Costs, Causes, Consequences, and Control, First Edition. V. S. Sastri.
© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.
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