Types of Corrosion

Uniform, pitting, galvanic, crevice, concentration cell and graphitic corrosion

Corrosion can be categorized in some common types

• uniform corrosion
• pitting corrosion
• galvanic corrosion
• crevice corrosion
• concentration cell corrosion
• graphitic corrosion

Uniform or General Corrosion

The metal loss is uniform from the surface.

Often combined with high-velocity fluid erosion, with or without abrasives.

Pitting Corrosion

The metal loss is randomly located on the metal surface.

Often combined with stagnant fluid or in areas with low fluid velocity.

Galvanic Corrosion

Occurs when two metals with different electrode potential is connected in a corrosive electrolytic environment.

The anodic metal develops deep pits and groves in the surface.

Crevice Corrosion

Occurs at places with gaskets, bolts and lap joints where crevice exists.

Crevice corrosion creates pits similar to pitting corrosion.

Concentration Cell Corrosion

Occurs where the surface is exposed to an electrolytic environment where the concentration of the corrosive fluid or the dissolved oxygen varies.

Often combined with stagnant fluid or in areas with low fluid velocity.

Graphitic Corrosion

Cast iron loosing iron in salt water or acids.

Leaves the graphite in place, resulting in a soft weak metal.

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