Positive Materials Identification

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Chapter 9

• Positive Materials Identification

Existing Material Identifications
Identification Methods Portable Quantitative
Analysis Laboratory Quantitative Analysis
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• Foundry marks are identification marks that are
  embossed on the exteriors of castings.

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• Color coding allows easy and rapid identification
  of metals, but systems can vary by company and
  location.

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• Stock materials are often stencil-marked along
  their lengths for identification.

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• Welding filler metals are identified by a
  standard AWS designation that is either stenciled
  or stamped directly onto the electrode or printed
  on a paper flag attached to the electrode.

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• Failure due to improper metal substitution
  outweighs the cost of implementing supplementary
  PMI programs.

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• Metals can be roughly identified and grouped by
  their characteristic colors.

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• Many metals can be identified and grouped by
  their magnetic behavior.

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• Coating thickness gauges identify unknown metals
  by comparing readings of unknown metals to
  readings of known reference metals.

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• A metal can be identified by measuring its
  density with an analytical balance.

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• Calculated densities can be used to place a metal
  in one of four groupings.

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• Spark stream characteristics are compared to
  spark charts to identify unknown metals.

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• Spark testing is most often performed on portable
  grinders, but stationary grinders may also be
  used.

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• Characteristic features of spark streams include
  carrier lines, forks, bursts, and arrowheads.

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• The electrographic chemical spot test is the most
  common chemical spot test.

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• Triboelectric sorting identifies unknown metals
  by measuring the voltage generated when two
  different metals are rubbed together.

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• Metallographic identification involves examining
  the microstructures of unknown metals to identify
  them. Specimen preparation requires grinding,
  polishing, and etching.

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• Replication tape is used to produce a replica of
  an unknown metal when it is impractical to
  examine the original specimen.

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• XRF analysis uses a detector that separates and
  identifies emitted X rays by either energy levels
  or energy wavelengths.

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• Many EDXA instruments are portable, allowing
  quantitative field identification.

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• WDXA instrumentation is not very portable because
  of the size of the X-ray generator and its
  cooling system.

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• OES uses the light emitted from an unknown metal
  surface for identification.