One of the best ways to help your bottom line, whether you’re a small company or large organization, is to define and restrict tolerances, especially as that applies to coating thickness and its subsequent measurement technology. In order to improve quality, lower costs and choose the best coating thickness gauge for your product, it is important to have a knowledge of the most common testing methods for coating thickness measurement.

The most popular methods include: X-ray fluorescence, magnetic induction, Hall effect, amplitude eddy current and phase-sensitive eddy current. X-ray fluorescence, or XRF, as its more commonly known, is an analytical technique used to determine the elemental composition of materials. It measures the fluorescent (or secondary) X-ray emitted from a sample when it is excited by a primary X-ray source. Each element has its own set of characteristic fluorescent X-rays, so XRF is an extremely accurate and beneficial test method for qualitative and quantitative analysis of a material.

For measuring specifically coat thickness, a method using XRF called energy dispersive X-ray fluorescence analysis (ED-XRFA) is used. ED-XRFA is particularly useful when measuring chrome, copper or nickel coatings applied over plastic, as ED-XRFA is capable of measuring each individual layer of the decorative chrome in the range of 0-5 microns or less, thus ensuring an incredibly exact measurement.

However, for paint thickness, the most commonly used measurement methods are magnetic induction, Hall effect, amplitude eddy current and phase-sensitive eddy current. Magnetic induction instruments, such as the MonitoRing, measure the thickness of metal with a low susceptibility to magnetization (not ferromagnetic) and the coatings of such metal, including: chrome, copper, zinc, paint and powder coating.

The QNix Gages used by Test Coat, Inc. employ the Hall effect and eddy current technologies. An eddy current is defined as a localized electric current induced in a conductor by a varying magnetic field. In the field of thickness measurement it is one of the electromagnetic testing methods used in nondestructive testing as it makes use of electromagnetic induction to discover and describe surface and sub-surface flaws in conductive materials.

The Hall effect can be described as the production of a voltage difference across an electrical conductor, crosswise to an electric current in the conductor and to an applied magnetic field vertical to the current. It is utilized to measure coating thickness by incorporating a small probe along with a strong magnet that creates a magnetic field around the sensor. A target then bends the magnetic field generated by the probe magnet, with the bending effect increasing as the target comes closer. Then a voltage across the Hall effect sensor is achieved. These voltage changes can then be translated into thickness readings.

Luckily, the average business owner or paint enthusiast doesn't need to fully comprehend the complex physics behind these tests. Having a working knowledge of which tests are currently being utilized for thickness measurement will suffice. In addition, the QNix gages used by Test Coats, Inc. do the hard work for you. All you have to worry about is ordering the best thickness measurement products and what you’re going to do with all the money they saved you!