Definition
of Discipline Activities: Failure Analysis & CorrosionDefinition
of Discipline Activities: Failure Analysis & Corrosion
One
of the functions of the metallurgical engineer is to develop extensive experience
with the environmental degradation of metallic materials, alloys, and nonmetals
due to corrosion or other physiochemical processes. This experience must involve
evaluating and solving corrosion-related failures of components, equipment,
and structures in the chemical process, refining, oil & gas, and pulp
& paper industries. The failures can range from the corrosion of surgical
instruments, automobile oil filters, ammunition cartridges, automobile air
bags, golf clubs, coatings, and even ice cream manufacturing equipment. Such
corrosion and environmental degradation mechanisms include: electrochemical
corrosion, uniform corrosion, acidic corrosion, alkali corrosion, aqueous
corrosion, intergranular corrosion, intergranular cracking, rusting, weld
corrosion, localized corrosion, oxygen corrosion, hot corrosion, stress corrosion
cracking, corrosion fatigue, hydrogen embrittlement, hydrogen sulfide corrosion,
microbiological corrosion, carbon dioxide corrosion, erosion-corrosion, elevated-temperature
corrosion, oxidation, sulfidation, and carburization.
These corrosion mechanisms and their root cause solutions have been studied
in most of the commercial alloys and metals including cast irons, carbon steels,
low-alloy steels, stainless steels, including the austenitic, ferritic, martensitic,
precipitation hardening, and duplex stainless steels, nickel and nickel alloys,
copper and copper alloys, and aluminum and aluminum alloys.
Failure analysis involves metallurgical investigations
of components, equipment, metals, alloys, coatings, linings and structures
due to corrosion, environmental degradation and abuse, misapplication of the
particular metal, and mechanical failure. Experience with failure analysis
is particularly strong in the chemical processing, refining, oil & gas,
and pulp & paper industries. Failure mechanisms evaluated usually include:
general corrosion, localized corrosion, intergranular corrosion, weld corrosion,
stress corrosion cracking, fatigue, corrosion fatigue, fretting, wear, erosion,
overload, brittle fracture, hydrogen embrittlement, hydrogen sulfide cracking,
microbiological corrosion, oxidation, sulfidation, and carburization. These
failure types have been investigated in such diverse components as pressure
vessels, welded fabrication, piping, heater and boiler tubes, marina docks,
storage tanks, drums, towers, columns, pumps, heat
exchangers, forgings, bearings, compressors, and gearboxes.
Another fuction of the metallurgical engineer is to apply, when indicated,
non-metallic coating systems for the protection of equipment and structures
from corrosion and environmental degradation. Over the past 10 years, a major
emphasis has been on the specification of coating systems for severe service,
including immersion service in corrosive environments and for concrete containment
structures in hazardous waste storage tank systems.
Experience with coating system recommendations and failure analysis of such
coating materials as the epoxies, urethanes, organic zincs, alkyds and silicones
are prerequisites for credible investigations, as is developing coating system
application and inspection specifications for industrial users in the U.S.
and overseas.
The metallurgical engineer must have knowledge of material and corrosion properties, metals and alloy testing and inspection for applying to evaluations on suitability-for-service, remaining life, and mechanical integrity of equipment. Furthermore, a risk-based inspection procedure is necessary to rank process equipment based on the probability of internal failure. This procedure helps companies meet the mechanical integrity requirements of OSHA's 1910.119, Process Safety Management regulations.
Corrosion investigations can also involve source identification in ground-water contamination and in chemical analyses of a variety of samples taken, both soil and ground -water samples. Thus, an interdisciplinary team of scientists and engineers would be brought to bear in projects involving water supply and ground-water remediation. Such forensic activities may also extend to hydrogeologic and and other forensic investigations involving getotechnical and other natural resource assessments.
For further information on the discipline, the Institute
of Environmental Technology sponsors an Internet Resources Portal, click (here).
The ELA Principal responsible for failure analysis and corrosion studies of tanks and other equipment is:
Note: The environmental field is multi-disciplinary by nature and, for maximum effectiveness, ELA incorporates input from complimentary disciplines when appropriate in most projects undertaken.
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Last Update: November 23, 1997