Environmentally induced cracking

Question 1

What is EIC?

Answer 1

corrosion due to mechanical stresses and corrosive environment; includes stress corrosion cracking, corrosion fatigue, hydrogen induced cracking, and liquid metal embrittlement

Question 2

–>What are the general characteristics of stress corrosion cracking?

Answer 2

> cracks propogate under tensile stress
cracking generally restricted to specific metal/environment conditions
in general alloys are more susceptible to metals
specific environments cause SCC
SCC is brittle in macroscopic appearance

Question 3

What are the stages of environmental induced cracking?

Answer 3

1. crack initiation
2. steady growth
3. final fast fracture

Question 4

Crack initiation process

Answer 4

> localized breakdown of passive oxide film due to mechanical damage or chemical attack
cracks usually start at surface discontinuities

Question 5

Hydrogen embrittlement

Answer 5

> can be easily picked up by metals during melting,
casting, working, electroplating, welding,
fabrication and use
minute amounts can damage metals