The corrosive action eats into the tube metal, removing iron and resulting in thinner tube walls.

If this action is allowed to continue, certain tubes will fail and will rupture, as the thinner section of tube can no longer withstand the internal operating pressure.

The removed metal, products of corrosion, can also cause a problem, as this material now increases the total quantity of solids contained in the boiler water.

As we know, this can increase the probability of deposits and scale formation on the inside wall of the tubes.

So what are the conditions that cause corrosion and loss of metal inside the boiler drums and boiler tubes?

Well, there are basically three independent causes of corrosion, and they are Acid attack, which occurs when the boiler water is in an acidic condition, that is, low pH.

Caustic attack, which occurs when the alkalinity of the boiler water is too high.

The pH level is above about 10.5.

The presence of dissolved gases such as oxygen and carbon dioxide in the boiler water.