Governing specifications and work procedures often dictate the penetrant method type. Selection of the penetrant method is based on the part’s end use, safety considerations, part composition, surface finish, and any important factors specific to the part. Selection of the correct penetrant method is important to not only comply with specifications but to detect surface breaking indications on the parts easily. The selection of the correct penetrant method along with the correct sensitivity level will result in confidently detecting the indications that can be found in the inspected parts
• Method A: Water washable
• Method B: Post emulsifiable, lipophilic
• Method C: Solvent removable
• Method D: Post emulsifiable, hydrophilic
1. Review governing specifications and work procedures
Often the penetrant method and sensitivity level are called out in the specifications and work procedures. In this case, the proper Sunlonge penetrant products can be selected based on method and sensitivity level with confidence that the Sunlonge products will meet the industry quality standards.
2. In the case where the penetrant method and sensitivity level is not specified, consider the following
Surface roughness and finish – Method A Water. Washable penetrants perform well on rough surfaces. Common applications include automotive castings such as steering knuckles, subframes, and housings.
Higher sensitivity penetrants (Methods A, B, D) are suitable for highly machined surfaces and safety critical parts.
3. Penetrant evaluation on actual test parts
Sunlonge recommends an evaluation on actual test parts with a few penetrants to determine the best choice penetrant for an application where the penetrant method and sensitivity level are not dictated in guidance documents. An evaluation on actual test parts establishes proper penetrant sensitivity and brightness with acceptable background fluorescence to detect the type of indication typically found on the parts. An evaluation on actual test parts will also establish the optimal processing parameters (dwell time, rinse time, dry time, developing time) for a given part.