Deposition

Definition

Deposition is the encompassing term for any foreign material covering a metal surface, including corrosion byproducts, scale, biofouling, and suspended solids. It indicates the surface is shielded by a foreign layer.

Whatever its source, a deposit creates a localized oxygen-depleted region beneath it, which sets up the conditions for oxygen differential corrosion. Deposits in cooling towers behave like pits, with the covered metal anodic and the exposed metal cathodic. Deposition is therefore a precursor and enabler of under-deposit corrosion.

Related concepts

Oxygen Differential Corrosion · Biofilm · Suspended Solids

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