Hydrogen Generated During Operation

In general, steel in concrete operates in the interval of potential and pH outside the critical ranges for hydrogen evolution. Under particular conditions, however, the situation may be different. Situations that make it jxtssible for hydrogen to develop are localized corrosion on the reinforcement that lead to oxygen depletion (and thus depresses the potential), acidity production at the anodic zones, and external cathodic polarization applied to the steel (due to, for example, excessive cathodic protection or stray currents). 

Carbonated concrete. The pH of carbonated concrete falls to values just slightly above 8 and so the critical threshold for hydrogen evolution rises to —700 mV SCE. In aerated carbonated concrete the potential of reinforcement reaches values between —300/—500 mV SCE and thus hydrogen evolution cannot take place (zone 

Concrete containing chiorides. Inside corrosion pits that can develop in chloride- 

Considerations analogous to those used for cathodic protection are also valid for the action of stray currents (Chapter 9), in zones where the cathodic process occurs. 

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Explosions and fire may arise from electrical shorting, leaking fuel pipes, dust accumulation (spontaneous combustion) and from hydrogen generation during battery charging. The truck itself can be the source of ignition if operated in flammable atmospheres... 

Oi, T. and Sakaki, Y., Optimum hydrogen generation capacity and current density of the PEM-type water electrolyzer operating only during the off-peak period of electricity demand, J. Powr ource, 129, 229-237 (2004). 

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