balasparks said:
I want to study about Barrel Plating and alloy plating ,
Especially ,
1. Zinc plating on Iron ( Barrel plating )
2. Tin - Bismuth Alloy Plating with a copper base coat.(and how to find the thickness coated in microns ?- Can XRF do the needful)
please share the materials available for study purpose, if any...........
It will be really useful to me.
Although this is not a plating forum, someone here might be able to help you. I would, however, suggest you ask the questions on finishing.com. They could surely help you.
It should be no problem to find information on barrel plating zinc over steel on the internet
XRF can be used to determine the plating thickness, but only if you have a set of standards for that particular combination. I would think that, in obtaining the proper standards, there are 2 different things to consider - the ratio of the tin/bismuth in the alloy and the thicknesses of the plating on a copper substrate. In other words, if you had 2 samples of the same thickness, but with different Sn/Bi ratios, you would get 2 different thickness readings. I did find commercially made tin-bismuth foils of various alloy ratios. https://bowmanxrf.com/lead-frames-standards/
If I had this problem, I would probably make my own standards by analyzing the plating to determine the alloy ratio and then measuring the thickness by sectioning and optical measurement with a metallograph scale built into the optics. Actually, sectioning and optical measurement is probably a much more reliable method of measuring alloy plating than XRF or any other method. This is because of alloy variations from batch to batch.
If you're not familiar with sectioning, in involves the potting of a sample, edgewise, in a liquid plastic. The resulting hardened plastic chunk is usually about 1.5" in diameter and about an inch thick. When it hardens, one side is ground and polished to expose the edges of the plating layers. The differences in the appearances of the plating layers are further enhanced by selective etchants. The layer thicknesses are then measured with a scale built onto metallographic optics.
http://www.misumi-techcentral.com/tt/en/surface/2015/12/221-plating-thickness-test-by-microscopic-exam-of-cross-section.html
Although the use of X-ray for plating thickness measurement has been around for at least 50-55 years, I have never used it. I did use the much more popular beta-backscattering method extensively and I also have done a lot of sectioning. The beta-backscattering equipment has been pretty much phased out, probably because of the necessity of using radioactive isotopes. The isotopes I used were Pm-147 and Tl-204, if I remember right.
Another interesting plating thickness measuring device is the one made by Kocour. It uses various solutions for various different types of plating. It dissolves a spot of the plating about 1/8" in diameter, electrolytically. When the plating is dissolved enough to expose the next plating layer or, in the case where there is only one plating layer, the substrate, the amperage immediately changes and this automatically shuts off the machine. The thickness is determined by the time it takes to eat through the plating, as compared with standards of known thickness. This was especially handy when there were several plating layer, e.g., chrome on nickel on copper on steel, for things like car bumpers. The Kocour can measure the thicknesses of all three plating layers, individually. Of course, the Kocour method is destructive.
https://www.kocour.net/pdfs/uploads/6000ManualV.5.11.11_4_12_2011_10_44_13_AM.pdf
