Electrodeposition for digital image correlationMay 15, 2012
We are a group of researchers in materials science at a Canadian university.
Our main research is fracture of the materials, and strain paths. One of the techniques used to acquire and analyze our data is digital image correlation. For this technique to work (at micro and nano scales), we need to deposit small features (1 micron or smaller) on the surface of the metal that will be tested.
The 2 metals that we are testing right now are aluminium 5052, and interstitial-free steel.
We have been trying electrodeposition with copper for a while. It seems to work on aluminium samples (occasionally). Whereas, the steel samples get fully coated immediately as soon as they get inserted in the electrolyte (copper sulfate)
For best results, we are trying to obtain a dense, "small-dot" pattern on the sample, i.e., stop the deposition at the nucleation stage.
We don't necessarily need to use copper. It was just available in the lab, and we tried it. We use copper sulfate 1M solution with PEG added to it, and a DC source of current for a very short period of time (for aluminium samples). Our samples are very well polished and cleaned before the deposition.
Could you offer any advice on how to achieve reproducible results?
- Ottawa, Ontario, Canada
A. Unfortunately, you need slightly different processes to plate steel or aluminum with copper.
For steel, you need to use a cyanide or alkaline, non-cyanide copper plating solution.
Aluminum must first be coated with a layer of zinc (an immersion zincate process)or bronze before copper plating. Even with these steps, it is more common to use an alkaline copper bath for aluminum because the acid copper sulfate bath may strip off the zinc or bronze before copper deposition takes place, resulting in blisters.
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