Thermogalvanic Corrosion

What Does Thermogalvanic Corrosion Mean?

Thermogalvanic corrosion is a type of corrosion that results from the action of temperature differences in electrolysis. The two metal electrodes in an electrolyte have different potentials; hence, the anode corrodes more than the cathode. The potential difference between the two metals is determined from the listing of the standard equilibrium potentials. The standard potential is known to assume the standard metal surface in any given standard solution that contains its ions at unit concentration.

In practice, metals have films on their surfaces, and when exposed to non-standard environments, they result in unreliable potential guides for the two corroding metals. Thermogalvanic corrosion is encountered mostly in heat exchangers where there are temperature differences. The region with the higher temperature in the metal acts as the anode, and the cooler acts as the cathode. The anode undergoes high rates of thermogalvanic corrosion, which is associated with high temperatures.

Corrosionpedia Explains Thermogalvanic Corrosion

When the temperature of a material changes, the rate of corrosion also tends to change. This can be explained through this rule of thumb: A rise in temperature by 10°C doubles the rate of corrosion. When one component part is hotter than another, the thermal gradient accentuates the corrosion rate difference. The resulting attack of metal occurs in the zone in between the minimum and maximum temperatures.

Thermogalvanic corrosion can be prevented by using any of the following methods:

• Designing the component to reduce the thermal gradient
• Supplying a coolant in the component to minimize temperature differences
• Galvanic corrosion-resistant coatings made of steel alloys and iron. These are sacrificial coatings that slowly corrode while simultaneously minimizing steel corrosion. This prevention method has been used in bridges in coastal regions and wind energy windmills. Experts recommend this method, versus paints, as it provides longer protection.