Page 67 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

MECHANICALLY ASSISTED CORROSION 45

Mechanically Assisted Degradation

Erosion Cavitation
Flow
Bubbles

Fretting
Corrosion fatigue
Load

Vibr. Vibr.
Dynamic
stress

Figure 1.14 Corrosion types of mechanically assisted degradation. (Reproduced with
permission of NACE International from Reference 3.)

except vacuum and inert atmospheres. Corrosion and wear can combine and cause
damage in many industries, such as mining, mineral processing, chemical process-
ing, pulp and paper production, and energy production. Wear debris and corrosion
products formed during mineral processing operations can affect product quality and
subsequent beneficiation by altering the chemical and electrochemical properties of
the mineral (9).
Exposure to gaseous and humid environments affects mechanical properties, fric-
tion, and wear of polymers. Synergistic effects between abrasion, wear, and corrosion
result in amplified damage (59, 60). The dominant and synergistic influence of some
factors may be noted as follows.

1.7.2 Abrasion
This attack involves removal of protective oxidized metal and polarized coatings to
expose unoxidized metal as well as removal of metal particles. This results in the
increase of microscopic surface area exposed to corrosion. Strain-hardened surface
layers are removed. Cracks are located on brittle metal constituents resulting in sites
for impact hydraulic splitting. Plastic deformation by high-stress metal–mineral con-
tact causes strain hardening and susceptibility to chemical attack.

1.7.3 Wear Impact
Plastic deformation makes some constituents more susceptible to corrosion. Wear can
cause cracking of brittle constituents, tear apart ductile constituents to form sites for