Page 46 - CFCM Mar-Apr 2021_Neat

PLATING AND ANODIZING: THICKNESS TESTING

steel substrates. It measures non-conduc- rent. As the probe approaches a magnetiz-
tive coatings over ferrous substrates. These able substrate, a magnetic field is induced in
gauges are the go-to measuring appara- the substrate perpendicular to the current in
tuses in the e-coat and powder coating the detector coil. The strength of the voltage
industries but can also be used to measure produced is proportional to the distance
Anodized Aluminum.
nonmagnetic metals such as chrome or from the probe to the ferrous substrate,
zinc plated on steel. which in turn calculates coating thickness.
The most basic magnetic thickness Magnetic thickness gauges are often
gauge is composed of a permanent magnet- paired with eddy current gauges to allow the
ic and a spring. The magnet is attracted to instrument to measure non-conductive
the ferrous substrate and the force required coatings over both ferrous and non-ferrous
for the user to pull the magnet off the sub- substrates. These gauges are easy to use and
strate is correlated to the thickness of the have come down in price over the past few
coating; the less force required to pull the years as the technology has improved.
magnet off the substrate, the thicker the Each of the instruments discussed in
coating. While a coating thickness test this article are popular throughout the
cannot get any simpler than this analog surface finishing industry. By knowing the
Powder Coated Steel.
method, it is very sensitive to surface appropriate application of each instrument
roughness, substrate thickness and the and its limitations, operators can obtain
are examples of where eddy current gauges type of steel alloy used, therefore its accu- accurate and precise data about coating
are limited. Additionally, these instruments racy is limited. thicknesses. By controlling, maintaining
cannot be used on steel substrates which A more robust magnetic method is a and achieving the correct coating thick-
limits its applications in the surface finishing magnetic induction thickness gauge. These ness, surface finishing shops can control
industry. gauges use two coils inside its probe: a mag- their costs, maintain their quality and
netic coil and a detector coil. It operates by achieve the best possible finish. n
Magnetic Thickness Gauge adhering to the Hall Effect, which states that
A magnetic thickness gauge is a non- a voltage is produced when a magnetic field Connor Stewart, B.Sc., is Technical Sales
destructive technique that can be used on is applied perpendicular to the flow of cur- and Service Representative, Dynamix.

Coating Thickness Gages

NEW Design and Features

NEW Larger 2.8” impact resistant color touchscreen and redesigned keypad for quick
menu navigation
NEW Weatherproof, dustproof, and water-resistant—IP65-rated enclosure
NEW Updated user interface retains the same layout and menus
NEW Up to 30% longer battery life
NEW On-gage help explains menu items at the touch of a button
NEW Ergonomic design with durable rubberized grip
Backwards Compatibility!
Accepts ALL coating thickness, surface profile, environmental, soluble salt, hardness,
and ultrasonic wall thickness probes manufactured since 2012.

DeFelsko Corporation Ogdensburg, New York USA
Tel: +1-315-393-4450 www.DeFelsko.com

46 CANADIAN FINISHING & COATINGS MANUFACTURING MARCH/APRIL 2021