68
Fundamentals of Corrosion
revised periodically by the American Petroleum Institute; therefore,
the latest data should be used for the proper selection of steel.
2. Material selection. Steels containing 1 to 2.25% Cr and Mo are recommended for use in hydrogen atmospheres at high temperatures
because carbide-forming elements such as chromium and molybdenum increase the resistance of steel to hydrogen attack. Conversely,
the carbon content should be kept low because increased carbon
decreases the resistance of steel to hydrogen attack.
Stainless steels, particularly austenitic stainless steels, are immune
to hydrogen attack. However, atomic hydrogen will diffuse through
these steels when used as a cladding material and the steel substrate
will be prone to attack.
3.11 Liquid Metal Attack
Metallic components may come in contact with liquid metal during operations such as brazing, soldering, or galvanizing and in some applications
such as the use of molten sodium as a coolant in fast-breeding nuclear reactors. Liquid metal may corrode the solid metal component or there may be
diffusion-controlled intergranular penetration of liquid metal in the solid
metal. The most drastic form of liquid metal attack is the instantaneous fracture of the solid metal in the presence of stress, a condition described as
“liquid metal embrittlement” (LME). The flow behavior of the solid metal is
not sufficiently affected but a significant reduction in fracture stress or strain
is encountered.
The attack of solid metals by liquid metals may take place in the following forms:
1. Instantaneous failure of a solid metal under applied or residual
stresses when in contact with a liquid metal
2. When a solid metal is in contact with a liquid metal at a static stress
below the tensile strength of the metal, a delayed failure will occur
3. Stress-independent grain boundary penetration of a solid metal by a
liquid metal
4. High-temperature corrosion of a solid metal by a liquid metal
The first two types are generally referred to as liquid metal embrittlement
(LME) or liquid metal-induced embrittlement (LMIE).
Fundamentals of Corrosion
revised periodically by the American Petroleum Institute; therefore,
the latest data should be used for the proper selection of steel.
2. Material selection. Steels containing 1 to 2.25% Cr and Mo are recommended for use in hydrogen atmospheres at high temperatures
because carbide-forming elements such as chromium and molybdenum increase the resistance of steel to hydrogen attack. Conversely,
the carbon content should be kept low because increased carbon
decreases the resistance of steel to hydrogen attack.
Stainless steels, particularly austenitic stainless steels, are immune
to hydrogen attack. However, atomic hydrogen will diffuse through
these steels when used as a cladding material and the steel substrate
will be prone to attack.
3.11 Liquid Metal Attack
Metallic components may come in contact with liquid metal during operations such as brazing, soldering, or galvanizing and in some applications
such as the use of molten sodium as a coolant in fast-breeding nuclear reactors. Liquid metal may corrode the solid metal component or there may be
diffusion-controlled intergranular penetration of liquid metal in the solid
metal. The most drastic form of liquid metal attack is the instantaneous fracture of the solid metal in the presence of stress, a condition described as
“liquid metal embrittlement” (LME). The flow behavior of the solid metal is
not sufficiently affected but a significant reduction in fracture stress or strain
is encountered.
The attack of solid metals by liquid metals may take place in the following forms:
1. Instantaneous failure of a solid metal under applied or residual
stresses when in contact with a liquid metal
2. When a solid metal is in contact with a liquid metal at a static stress
below the tensile strength of the metal, a delayed failure will occur
3. Stress-independent grain boundary penetration of a solid metal by a
liquid metal
4. High-temperature corrosion of a solid metal by a liquid metal
The first two types are generally referred to as liquid metal embrittlement
(LME) or liquid metal-induced embrittlement (LMIE).