Liquid
Metal Attack
Description
Corrosive degradation
of metals in the presence of certain liquid metals such as mercury, zinc,
lead, cadmium. examples of liquid metal attack include: chemical dissolution.
metal-to-metal alloying (i.e. amalgamation). embrittlement and cracking.
Prevention or
Remedial Action
Standard Test
Methods
- ASTM G129 - slow
strain rate test for determination of environmentally assisted cracking.
- ASTM G-30 - practice
for making and using U-bend SCC test specimens.
- ASTM G-38 - practice
for making and using C-ring SCC test specimens.
- ASTM G-39 - practice
for preparation and use of bent-beam SCC test specimens.
Evaluation
for Liquid Metal Embrittlement (LME)
The evaluation of
LME usually requires chemical or mechanical techniques to overcome the
incubation period for cracking. In much the same way that a localized corrosion
event is needed to initiate SCC, local chemical attack is usually a precursor
for LME. Dynamically applied loads as in the slow strain rate test can
be used to break normally protective surface films to allow intimate contact
of the material surface and the liquid metal. Chemical agents can also
be used to remove or breach this surface films and initiate localized attack
so that the inherent susceptibility of the material can be determined.
In some cases, surface treatments may be utilized to enhance resistance
to LME. However, this should be conducted with extreme caution since damage
to this surface layer may induce cracking.
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