Pre-Penetrant Etch

Chemical Processing Method Applicability

Pre-Penetrant Etch, also known as Pre-Pen Etch, is a surface preparation process. It primarily removes smeared material to prepare a part for subsequent Fluorescent Penetrant Inspection (FPI) processing. Examples of processes that potentially smear material include grinding, sanding, abrasive blasting, buffing, reaming, milling, drilling, etc.

The type of cleaning process and solutions used depend upon the material of the metal part to be processed. The pre-pen etch process does remove a small amount of material and is closely controlled to do so. Typical target removals are on the order of 0.00005 in [0.00125 mm] per surface.

Pre-pen etch is only performed when specified to do so. It is not automatically performed by MTC before all FPI processing. It is the responsibility of the part manufacturer and/or part design authority to specify when a pre-pen etch is necessary.

MTC Metal Etching Laboratory Inspection Service

At Metals Testing Company, we have a complete in-house capability of equipment, chemicals, procedures, qualified personnel, waste treatment, environmental related permits, and industry certifications to accomplish high quality pre-pen etch processing.

The following are examples of pre-pen etch related specifications that MTC is approved to perform:

  • HS7725
  • RPS 15.45
  • C5098
  • MTV 607-3
  • SS8712 (swab etch)
  • EIM Code 8
  • RPS 674 (including swab etch)
  • CP3605

Common types of parts that MTC pre-pen etch processes include housings, brackets, rod ends, closures, actuators, pistons, flanges, valve bodies, retainers, yokes, balls, bearing plates,  core weldments, etc.. Note that critical rotating parts are not normally pre-pen etched as they are instead typically BEA, Anodic, or Chem Etched for their NDT inspection purpose.

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