Selective/Leaching Phase Attack

Description

Selective leaching/phase attack is the removal of one element from a metal or alloy by a corrosion process, similarly, this process can also selectively remove one phase from an alloy. The most common example of this form of attack is the removal of zinc (Zn) from brass alloys. In duplex stainless steels, some acidic environments can selectively remove either the ferrite or austenite in the microstructure.

Prevention or Remedial Action

• reduce severity of environment through environmental control or addition of effective chemical inhibitors.
• cathodic protection.
• use of coating to act as a barrier between the environment and the alloy.

Standard Test Methods

• ASTM G-31 - practice for laboratory immersion corrosion testing of metals.
• ASTM G-4 - method for conducting corrosion coupon tests in plant equipment.