---
title: Potential Reversal Phenomenon
description: Understand why ZnO/Zn(OH)₂ instability triggers potential reversal in galvanized steel, transforming sacrificial zinc into a corrosion-promoting anode.
---

[Glossary ](https://www.o2oh.com/glossary)

# [Potential Reversal Phenomenon](https://www.o2oh.com/glossary/potential-reversal-phenomenon)

 Written by [one to ONE Holdings](https://www.o2oh.com/glossary/author/one-to-one-holdings) | Feb 6, 2026 5:18:18 AM

The potential reversal phenomenon occurs when [**zinc**](https://www.o2oh.com/glossary/zinc), typically used to protect steel from corrosion through [**sacrificial protection**](https://www.o2oh.com/glossary/sacrificial-protection), instead accelerates the steel's corrosion.

Normally, zinc serves as the [anode](https://www.o2oh.com/glossary/anode) and protects steel, which acts as the [cathode](https://www.o2oh.com/glossary/cathode). During potential reversal, these roles switch: steel becomes the anode and corrodes before the zinc. Although some conditions for this phenomenon have been identified, they are not fully understood. Temperature, pH, and specific ions in water or soil are believed to play key roles.

Zinc maintains corrosion resistance below 50°C, but its corrosion rate rises sharply near 60°C, significantly reducing its protective effectiveness. In high-temperature and high-humidity environments, the rapid formation of zinc oxide (ZnO) and zinc hydroxide (Zn(OH)₂) destabilizes the material and triggers potential reversal. As a result, zinc in the galvanized layer promotes, rather than prevents, steel corrosion.

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