Study of the Coating Thicknesses Effect to the Length of the Indication via Magnetic Particle Testing

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Parvinee Angboonta
Paisan Thongson
Prajak Angboonta


This research aims to study the coating thicknesses on specimen effecting to the magnetic particle testing. The main studies variables are the coating thickness which study the three coating types, 1. White contrast coating, 2. Color coating, and 3. Lacquer coating. The research testes with the NA – 16 notch defect test bar of the wide size, the length size and the depth size 0.0060-inch, 0.0625-inch, and 0.0200-inch respectively. The experiment was conducted for indications on both uncoated test specimen and coated test specimen. The experiment tests the coated test specimen that has a low thickness until the thickness where a clear indication cannot be displayed. This research uses a ac – yoke for magnetizing the coated test specimen while spraying the fluorescent magnetic powder on the desired location to inspect. The images are recorded via a microscope at 30X magnification under UV – A light in a dark room.

The experimental results found that the thickness of the 3 types of coatings affected the amount of magnetic field intensity generated on the specimens of different coating thicknesses. The thickness of the coating that has the greatest and the least effect on the magnetic field strength are the white coating., the lacquer and the color coating respectively. The values of three coated types thickness affect the magnetic field strength are 61.19 µm, 73.63 µm, and 83.56 µm respectively. The coating thickness is acceptable when the length of the indication on the coated surface is at least 50% of the length of the corresponding indication prior to coating according to the Section V of ASME Code.


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The Welding Engineer’s Current Knowledge, GSI SLV, Duisburg, Germany, 2015, pp. 23–25.

M. Bahman, P. M. Mohammad, Y. Mojtaba, S. Hossein, S. O. Farzin, and A. Alireza, “Stochastic lifetime estimation of pressurized gas pipeline; Case study of the urban gas pipeline,” Int. J. COMADEM, vol. 20, no. 2, pp. 31–37, Apr. 2017.

J. T. Schmidt and K. Skeie, “Dry power magnetic particle tests of painted welds,” in Nondestructive Testing Handbook, 2nd ed. Columbus, OH, USA: American Society for Nondestructive Testing, 1989, pp. 386–387.

Y. Wang, X. Gao, M. Finckbohner, and U. Netzelmann, “The effect of paint coatings on detection of vertical surface cracks in metals by induction thermography,” NDT & E Int., vol. 104, pp. 58–68, Jun. 2019.

A. Keresten, S. Ostanin, and V. Zuev, “Advanced liquid epoxy and polyurethane materials: internal and external coatings for pipeline and tubing protection,” E3S Web of Conf., vol. 225, Jan. 2021, Art. no. 05004.

Non-destructive testing of welds — Magnetic particle testing, ISO 17638:2016, the International Organization for Standardization, Switzerland, Oct. 2016.

Parker Research Corporation. NA-16 Notch Defect Test Bar. (2023). Accessed: Dec. 28, 2022. [Online]. Available: https://

Magnaflux. WCP-2 White Contrast Paint. (2023). Accessed: Mar 13, 2023. [Online]. Available:

TOA Groups. Technical Data Sheet. (2017). Accessed: Mar 13, 2023. [Online]. Available:

TOA Groups. Technical Data Sheet. (2017). Accessed: Mar 13, 2023. [Online]. Available:

A. Prateepasen, Magnetic Particle Testing: Non – Destructive Testing in weld and research, 7th ed. Bangkok, Thailand: Chulalongkorn University Press (in Thai), 2014.

C. W. Eick, “Electrically Inducing Magnetism,” in ASNT Level II Study Guide: Magnetic Particle Testing Method, C. M. Leeman, Ed. Columbus, OH, USA: ASNT, 2017, pp. 15–19.

L. Stein, “Random patterns,” in Computers and You, J. S. Brake, Ed. New York, NY, USA: Wiley, 1994, pp. 55–70.

The American Society of Mechanical Engineers, “Article 7: Mandatory Appendix I,” in ASME Boiler and Pressure Vessel Code, New York, NY, USA: ASME Press, 2021, sec. V.

J. D. Fenton, “Magnetic Particle Testing: Magnetic Particle Testing Fundamentals,” in ASNT Level III Study Guide: Magnetic Particle Testing Method, 2nd ed. Columbus, OH, USA: ASNT, 2013, p. 1.