Quantitative measurement of Al2O3 powder contamination

Hi Guys,
I have a system where I use some Al parts, and sometimes I get a white powder that seems to be Al2O3. This powder is not distributed
uniformly, and it is a very thin layer. The problem that we have is that by looking at it you cannot quantify the amount of powder on these parts. Some of my colleagues say this part looks better than the other one, other say the opposite.
I would like to find a way to quantify the amount of powder. These parts are not disposable, so I cannot cut them or sent them out for analysis.
I am more of an optical guy, I am thinking of using an optical method, such as reflectivity or a similar method to measure the thickness/density of the powder, but if you have other ideas in mind please let me know.
Thanks chibitul p.s. if there is a better newsgroup, please let me know
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You could use some transfer and stripping technique, by applying a thin layer of a cellulosic cement on your metal surface. Let evaporate the solvent and harden completely, then strip the deposited sheet. It can be examined under the light microscope. Transmitted light will be better than reflected light, if you use dry objectives, but if you can observe under a hight mag. oil immersion objective(100x) and crossed polarizers, you should clearly see alumina particles thanks to their high light dispersion.
Quantitative data should be possible to get by putting the stripped layers directly in a fluorescence X-ray spectrometer or an EDS.
Membrane filters have also been used for stripping powders from surfaces. Polycarbonate- and cellulose ester-based membranes need of course different softening solvents.
J.J.
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