Thermogalvanic Currents in Steel Reinforced Concrete

• Temperature gradients generate galvanic currents, due to changes in cement chemistry and passive layer.
• 30 °C is the critical temperature for switching polarity of galvanic couples between steel rebars.
• In NaOH solution carbon steel behaves cathodically with respect to stainless steel for T < 30 °C.
• Temperature gradients enhance galvanic coupling in rebar’s corrosion.

The thermogalvanic currents between nominally identical segments in a reinforced concrete beam were investigated. Temperature gradients induce galvanic currents that exhibit a 30 °C critical point. The character of the hot electrode side changes from anodic to cathodic when the temperature rises above that pivot point. Parallel tests performed in solution using carbon steel-stainless steel galvanic couples also revealed that 30 °C is a critical temperature. In NaOH solution the carbon steel behaves cathodically with respect to stainless steel but only for T< 30 °C. In Ca(OH)2 solution containing chlorides the carbon steel consistently behaves anodically while the degree of thermogalvanic current exhibits a pronounced temperature dependence.

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