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Measuring Plating thickness

Measuring Plating thickness

Measuring Plating thickness

What is an easy way to measure plating on a steel or copper bar in microinches?  Does anyone know where to purchase such a device or company that we can send the parts to.

thanks in advance.

RE: Measuring Plating thickness

It depends very much on what your plating is, since measurement (other than by mechanical methods such as micrometer) depends upon the difference in physical properties between the substrate and the coating.  For instance, a magnetic gage can be used for measuring a non-magnetic coating on steel, or for a magnetic coating on copper, but not for magnetic on steel or non-magnetic on copper.
Also, if you are measuring a multilayer coating, say Cu+Ni+Cr on steel, you probably need an X-ray fluorescence machine with some powerful computer software to deconvolute the curves.
I suggest you start with the review articles below which include tables showing which instruments can measure which coatings:

Measuring Coating Thickness [rather brief]

Thickness Testing [makes the point that you must have proper standards, e.g., "Zinc plated in cyanide, chloride, or alkaline baths is the most prominent example of this problem [improper thickness standards]. Calibrating the instrument with standards from the same or similar solutions can greatly reduce error."

Some thickness tester vendors
(scroll down to thickness testers at the following link)

Automation USA
CMI International
DeFelsko Corp
Eastern Applied Research Inc
Elektro Physik USA Inc
Fischer Technology
Kocour Co
Magne-Gage Sales & Service
Paul N Gardner Co Inc

RE: Measuring Plating thickness

Also check ASTM B659, it gives the references to all the ASTM coating thickness measurement methods:

"B659-90(1997) Standard Guide for Measuring Thickness of Metallic and Inorganic Coatings
1. Scope

1.1 This guide outlines the methods for measuring the thickness of many metallic and inorganic coatings including electrodeposited, mechanically deposited, vacuum deposited, anodic oxide and chemical conversion coatings.

1.2 This guide is limited to tests considered in ASTM standards and does not cover certain tests that are employed for special applications.

1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

B244 Test Method for Measurement of Thickness of Anodic Coatings on Aluminum and of Other Nonconductive Coatings on Nonmagnetic Basis Metals with Eddy-Current Instruments
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of a Cross Section
B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals
B504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
B530 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Electrodeposited Nickel Coatings on Magnetic and Nonmagnetic Substrates
B567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B588 Test Method for Measurement of Thickness of Transparent or Opaque Coatings by Double-Beam Interference Microscope Technique
B767 Guide for Determining Mass Per Unit Area of Electrodeposited and Related Coatings by Gravimetric and Other Chemical Analysis Procedures
ISO Standard 1463: Metal and Oxide Coatings-Measurement of Thickness by Microscopic Examination of Cross Section
B681 Test Method for Measurement of Thickness of Anodic Coatings on Aluminum and of Other Transparent Coatings on Opaque Surfaces Using the Light-Section Microscope"


RE: Measuring Plating thickness

I have a part of electroless nickel-plated aluminum.

 They looked good as received, two months after I applied coating, pinholes showed up.

Are there method to detect the pinholes or plaing uniformity?



RE: Measuring Plating thickness

Porosity/pinhole tests for electroless nickel plating are given for iron-based, aluminum and copper substrates in paragraph 9.6 of ASTM B733.  The alizarin indicator test for aluminum substrates involves some chemistry but only takes about 10 minutes, and can thus be used for QC testing by the plater.  Pinholes show up as red spots.

The book Electroless Plating:  Fundamentals and Applications by Mallory and Hadju gives some additional methods, but none better than the alizarin test for aluminum substrates.

Is your part used in a corrosive environment?  Maybe the holes developed as a result of corrosion and would thus not be detected immediately after plating.  The alizarin method is suitable for testing sample parts exposed for various periods although I haven’t heard of anyone doing so.
Porosity would be detected by the 100 hour salt spray test if plating per MIL-C-26074E  (although this is a monthly process qualification test rather than a job lot test).

RE: Measuring Plating thickness

Electroless nickel has considerable variations in stress.  "Shiny" electroless nickel is extremely hard and high in stress.

You might be getting cracking in the coating or substrate, requiring some post-deposition annealing to relieve the stress.


RE: Measuring Plating thickness

Thanks for the great advice. I will try the chemical.

No, the part is just sitting there with my coating on, then the pinholes showed, becasue my coating is clear. The pits shows as pink color with bubble.


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