What will cause pitting of boiler metal?

Pitting of boiler metal is primarily caused by localized corrosion processes, which can be exacerbated by the presence of oxygen in the boiler water. When dissolved oxygen is present, it can lead to the formation of pits on metal surfaces. These pits create localized areas where corrosion is intensified, often due to a concentration of electrolytes in the small volume of water within the pits.

In boiler systems, dissolved oxygen can enter through various means, such as improper treatment of boiler water or leaks in feedwater systems. When oxygen comes into contact with the heated metal surfaces, it reacts and initiates corrosion at those specific spots, resulting in pitting. This type of corrosion can become a significant concern as it can lead to structural integrity issues within the boiler over time.

While other factors like heat and pressure can affect the overall corrosion rate and the general deterioration of boiler components, they do not specifically lead to pitting in the same way that oxygen does. Corrosion itself is a broad term that encompasses various types of metal degradation, but in this context, the focus is on the particular role of dissolved oxygen in creating localized corrosion that results in pits.