Eddy Current UPA Dermitron Eddy Current and Magnetic Induction
Eddy Current is a highly versatile measurement technique which is used in many industries to measure platings or coating thickness. Dermitron advanced Eddy Current instruments are used worldwide by platers, vacuum coaters, anodizers and metal finishers, wherever precise control of coating thickness is required. Most common usage is for the measurement of zinc/steel in the fastener markets for determining corrosion protection.
The UPA Dermitron uses Eddy Current (phase sensitive) technology to non-destructively and instantly measure metal plating thickness on ferrous, non-ferrous or even on plastic and ceramic substrates. Non-metallic coatings can be measured on any non-ferrous metals. Eddy Current measurements are made by inducing a high frequency Eddy Current onto a metal surface. Measurements are possible using phase sensitive Eddy Current whenever the electrical conductivity of the coating sufficiently differs from the base metal. This versatile technology can also be used for measuring metallic coatings on non-conductive substrates or even non-metallic coatings on metallic substrates.
Eddy Current calibrations are commonly done using plated standards. Since measurement is determined based on the plating deposit conductivity, the standards should ideally be plated from the same or similar plating bath to obtain the same conductivity of the plating deposit on the standards. The plating bath can have a major effect on the resulting measurement. For example; Alkaline or Acid Chloride plated parts must be calibrated using the correct bath. Errors of over 50% can occur from calibrating using incorrect standards for calibration. UPA Technology can plate custom calibration standards from customer plating baths to obtain the best accuracy and the closest correlation to XRF measurements.
Eddy Current instruments can be used directly on the plating line for point of process inspection. Instruments are virtually sealed, limiting the effects of the environment. Eddy Current accuracy is typically within @ ½ micron compared with X-ray. Nickel/Steel can also be measured by Eddy Current (phase sensitive), but the calibration standards should be made from the same plating bath to obtain the best results.
Common Applications
- Zinc/Steel
- Cadmium/Steel
- Silver/Stainless Steel
- Copper/Steel
- Nickel/Steel
- Vacuum deposited aluminum or copper on plastic
- Anodizing/Aluminum, Nitride case depth
Corrosion Protection for the Fastener Industry
Fasteners, nuts bolts and screws are plated to protect against rust and corrosion. The zinc plating thickness corresponds to how resistant to rust they will be. Higher quality requirements and longer warranties require the fastener industry to confirm that the thickness of the plating meets specifications. The rugged Dermitron can be used directly on the plating line or in the lab.
Measure Anodizing on Aluminum
Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, oxide finish. Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium can also be anodized. The anodic oxide structure originates from the aluminum substrate and is composed entirely of aluminum oxide. This aluminum oxide is not applied to the surface like paint or plating, but is fully integrated with the underlying aluminum substrate, so it cannot chip or peel. Since anodizing is a non-conductive oxide layer over conductive aluminum, anodizing is an easy measurement using Eddy Current.
Vacuum Coatings on Plastic Parts
Very thin metal vacuum deposited metals on plastics or ceramics can also be measured using Eddy Current. Copper and aluminum are commonly applied to plastic as RFI and EMF coatings and each are measured instantly with the Dermitron.
The Method
Eddy Current vs Magnetic Method
Phase Sensitive Eddy Current is better suited than magnetic methods for measurement of Zinc on Steel because of its ability to measure thin platings, even on rough surfaces and small or large parts. It also offers great advantages in measuring small objects since the probe’s measuring area can be reduced so that geometry of the part being measured has little influence on the measurement. Even the thickness of copper on steel BBs can be accurately measured without the need for probe stands or parts fixturing using Eddy Current! This measurement wouldn’t be possible using magnetic induction.
Click here to read an article about the advantages of using Eddy Current for measuring zinc plating compared to magnetic instruments for fasteners.
Probe Selection
| Coating Base | Probe | Range Mills | Range Micron |
|---|---|---|---|
| Zn/Fe (Cyanide) | C | 0-.65 | 0-17 |
| Zn/Fe (Cyanide) | B | 0-1.5 | 0-38 |
| Zn/Fe (Chloride) | C | 0-1.1 | 0-28 |
| Zn/Fe (Chloride) | B | 0-2.5 | 0-64 |
| Zn/Fe (Alkaline) | C | 0-1 | 0-25 |
| Zn/Fe (Alkaline) | B | 0-2 | 0-50 |
| Cd/Fe | C | 0-0.8 | 0-20 |
| Cd/Fe | B | 0-1.6 | 0-41 |
| Cu/Fe | C | 0-0.2 | 0-5 |
| Cu/Fe | B | 0-0.4 | 0-10 |
| Watt’s Ni/Fe | C | 0-0.5 | 0-13 |
| Watt’s Ni/Fe | B | 0-1.0 | 0-25 |
| Watt’s Ni/Fe | A | 0-2.0 | 0-50 |
| Brite Sn/Fe | C | 0-0.9 | 0-22 |
| Brite Sn/Fe | B | 0-2.0 | 0-50 |
| Cu/Non-Conductives | B | 0-0.6 | 0-15 |
| Cu/Non-Conductives | A | 0-2.0 | 0-50 |
| Non Conductives / Non-Magnetics | C | 0-33 | 0-840 |
| Non Conductives / Non-Magnetics | B | 0-40 | 0-1000 |
| Non Magnetic/Magnetic | ASP-3 | 0-32 | 0-810 |
Talk To An Expert
When you call UPA, you will speak with a real person who will direct you to a product or technical specialist to answer your questions, assist with your requirements or provide applications support.
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UPA Technology
8963 Cincinnati-Columbus Rd.
West Chester Ohio, 45069
Phone: 513-755-1380
Email: info@upa.com