58
Fundamentals of Corrosion
initially present in the metal or it may accumulate through absorption. In
most cases, the damage is associated with residual or applied stresses. The
damage may be in the form of:
1. Loss of ductility and tensile strength
2. Sustained propagation of defects at stresses well below those
required for mechanical failure
3. Internal damage due to defect formation
4. Macroscopic damage, such as internal flaking, blistering, fissuring,
and cracking
Hydrogen damage has occurred in many metals and alloys. High-strength
steels are particularly vulnerable, and there have been many instances of failure of oil drilling and other equipment made of high-strength steels working
in “sour” oil fields as a result of hydrogen damage. All types of stainless
steels, aluminum, copper, nickel, and their alloys; titanium and zirconium
alloys; and refractory materials such as tungsten, niobium, vanadium, and
tantalum are subject to hydrogen damage.
3.10.1 Sources of Hydrogen
Metals are capable of absorbing hydrogen from various sources. Atomic
hydrogen, rather than molecular hydrogen, is considered responsible
for the damage. However, atomic hydrogen may be absorbed from a
molecular hydrogen gas atmosphere. Hydrogen is readily available in
environments such as water, water vapor, moist air, acids, hydrocarbons,
hydrogen sulfide, and various liquids and gases utilized in chemical process operations.
Hydrogen damage may be produced during several stages of equipment
manufacture even before the equipment is placed into service. Hydrogen can be
introduced into the lattice of the metal during welding, heat treating in hydrogencontaining furnace atmospheres, acid pickling, or electroplating operations.
Underbead cracking is an embrittlement phenomenon associated with
hydrogen pick-up during welding operations. Hydrogen entry into metal
results from moisture in electrode coatings, high humidity in the atmosphere, and organic contaminants on the surface of prepared joints. Upon
rapid cooling of the weld, entrapped hydrogen can produce internal fissuring and other damage.
During acid pickling or electroplating, and as a result of corrosion in
service, atomic hydrogen is generated on the metal surface as a cathodic
reduction product that diffuses into the bulk material. When the material is
stressed, the diffusion rate is particularly high. In the pickling·of steel, the
level of hydrogen absorption depends on both the bath temperature and the
nature of the acid.
Fundamentals of Corrosion
initially present in the metal or it may accumulate through absorption. In
most cases, the damage is associated with residual or applied stresses. The
damage may be in the form of:
1. Loss of ductility and tensile strength
2. Sustained propagation of defects at stresses well below those
required for mechanical failure
3. Internal damage due to defect formation
4. Macroscopic damage, such as internal flaking, blistering, fissuring,
and cracking
Hydrogen damage has occurred in many metals and alloys. High-strength
steels are particularly vulnerable, and there have been many instances of failure of oil drilling and other equipment made of high-strength steels working
in “sour” oil fields as a result of hydrogen damage. All types of stainless
steels, aluminum, copper, nickel, and their alloys; titanium and zirconium
alloys; and refractory materials such as tungsten, niobium, vanadium, and
tantalum are subject to hydrogen damage.
3.10.1 Sources of Hydrogen
Metals are capable of absorbing hydrogen from various sources. Atomic
hydrogen, rather than molecular hydrogen, is considered responsible
for the damage. However, atomic hydrogen may be absorbed from a
molecular hydrogen gas atmosphere. Hydrogen is readily available in
environments such as water, water vapor, moist air, acids, hydrocarbons,
hydrogen sulfide, and various liquids and gases utilized in chemical process operations.
Hydrogen damage may be produced during several stages of equipment
manufacture even before the equipment is placed into service. Hydrogen can be
introduced into the lattice of the metal during welding, heat treating in hydrogencontaining furnace atmospheres, acid pickling, or electroplating operations.
Underbead cracking is an embrittlement phenomenon associated with
hydrogen pick-up during welding operations. Hydrogen entry into metal
results from moisture in electrode coatings, high humidity in the atmosphere, and organic contaminants on the surface of prepared joints. Upon
rapid cooling of the weld, entrapped hydrogen can produce internal fissuring and other damage.
During acid pickling or electroplating, and as a result of corrosion in
service, atomic hydrogen is generated on the metal surface as a cathodic
reduction product that diffuses into the bulk material. When the material is
stressed, the diffusion rate is particularly high. In the pickling·of steel, the
level of hydrogen absorption depends on both the bath temperature and the
nature of the acid.