24-Aug-2015, 09:18
The hardness/softness of aluminum remains identical before/after blasting. The softness is actually the result of both soda, sand or media blasting and the series of peaks and valleys blasting imparts to the surface. The peaks separated by valleys will be softer without support around them a solid surface offers when surrounding them. You could use any of those blast medias on a number of soft metals with the same result, ie; copper, lead, gold, silver etc. Yet harder metals and glass wouldn't have the same risk issues related to marring or burnishing at typical fingerprint influencing levels. Surfaces like glass, steel, stainless steel etc would remain unaffected by fingerprints. Under a microscope a blasted surface of any material would appear to be a series of millions of tiny peaks and valleys per sq inch. Because the 'peaks' are so tiny/soft they can be burnished with something soft as a fingerprint. That is to say those peaks can be rolled over sideways or made flatter by a fingerprint under pressure than the surrounding area whereas other substrates like glass, steel etc are left unmarred by things like fingerprints on a blasted surface due to hardness. But for thermal heat dissipation the coarse blasted surface is to be much preferred as it simply has far more surface area per sq inch to shed its heat compared to a flat or polished surface. In 2 dimensions imagine a straight line and an erratic frequency going across a 3" screen width. The frequency line will be MUCH longer if stretched out, have MUCH more surface area on its top. Due to the surface hardness of anodizing and aluminum oxide the relatively soft blasted surface fragility disappears afterwards same as if a coat of epoxy were sprayed on it only many, many times harder than epoxy. But unlike a hard coating that flows over the peaks and settles into the valleys between them and forming a thick insulative layer the anodized surface allows the enhanced cooling effect of increased peak & valley surface area to be retained with its associated enhanced cooling benefit. Only now the previously soft peaks are more like glass/steel than aluminum in hardness with no accompanying insulative layer. A good analogy might be imagine a heat sink filled with epoxy to overflowing between all its fins & pins and left to cure alongside a normal heat sink with good airflow between its fins/pins and how each of them might work and compare to each other as an effective/efficient heat sink.
Statements in my posts are opinion only, not to be construed as fact. Any projects I engage in are at my own risk! Their outcome cannot be assured and may result in success, small/no change or catastrophic failure. I encourage no one rely on anything I say or do as gospel and to realize your mileage may vary!
