Caustic Gouging

Caustic Gouging (Generally as a result of scale and sludge)

Caustic gouging can be found when localised boiling occurs beneath porous sludge deposits on the boiler tube.

The mechanism is simple, the water under the sludge turns to steam and boiler water is

drawn in to replace it, this contains salts including caustic, the boiling continues and the caustic concentrates very rapidly.

Caustic levels beneath the sludge of 100,000 ppm is not unknown.

High levels of caustic dissolve the protective metal oxide layer on the surface of the boiler tube.

The oxide re-forms but is immediately dissolved again.

The result is a distinctive gouged pattern of metal removal which eventually leads to failure

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