Both the FAA and CASA have issued warnings to advise personnel involved in using liquid penetrant for non-destructive inspection of the unsuitability of visible dye penetrant – predominately colored red – for final inspection of safety critical components.
The portability, low cost and ease of use of visible (usually red) dye penetrant has seen this type of penetrant system become the preferred option for many personnel inspecting safety critical components. However, ASTM E 1417 ‘Standard Practice for Liquid Penetrant Testing’ prohibits Type II visible dye systems for final acceptance of inspection for aerospace products. In addition to the above limitation, ASTM E 1417 also prohibits the use of visible dye penetrant before inspection using a Type I fluorescent dye penetrant system. The chemical properties of the solvents contained in Type II visible dye penetrant ‘quench’ or destroy the fluorescence (glowing) of Type I fluorescent dyes, degrading both the sensitivity of an inspection and the accuracy of any
result. .
National Airworthiness Authorities and Non-Destructive Testing professionals are concerned about the trend in using Type II visible dye penetrant for final inspection of safety critical aircraft components and materials contrary to the standards published for the penetrant system. The FAA was so concerned they issued a memorandum in 2000 to highlight the issue of using visible dye penetrant for final inspection of safety critical components.
