How does oxygen contribute to boiler metal degradation?

Oxygen contributes to boiler metal degradation primarily through its role in supporting chemical reactions that lead to pitting corrosion. In a boiler system, when oxygen is present in the water, it can react with iron and other metals that make up the boiler. This reaction typically results in the formation of iron oxides, which can manifest as pitting—a type of localized corrosion that creates small holes or cavities in the metal surface.

The presence of oxygen accelerates these corrosive processes because it is a powerful oxidizing agent. As the metal oxidizes, protective layers that might normally inhibit further corrosion can be compromised, leading to additional damage. This mechanism is particularly problematic in areas where water flows are turbulent and oxygen levels can fluctuate, increasing the likelihood of pitting and overall metal degradation.

In contrast, options that suggest enhancing metal purity, improving operational efficiency, or reducing temperatures do not accurately depict the damaging effects of oxygen in the context of boiler maintenance and operation. Instead, they suggest scenarios where oxygen would have beneficial effects, which is not the case concerning boiler metal integrity.