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| a (mostly) invisible difference between my civilian & military Fluke gear |
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| sokoloff:
--- Quote from: Fungus on October 30, 2022, 01:44:43 pm --- --- Quote from: Wrenches of Death on October 30, 2022, 01:30:17 pm --- --- Quote from: Fungus on October 30, 2022, 12:13:08 pm ---Why would they add 1/4 inch of heavy paint to aluminum? --- End quote --- Everything had been painted dozens and dozens of times over the decades. --- End quote --- I wouldn't have thought that aluminum needed any painting. It doesn't rust and it already comes in battleship grey color. Still: There's the right way, the wrong way, and the military way... --- End quote --- Exactly. There's a happy overlap in mission between "these things need painting in order to protect them" and "these enlisted painters need things to paint in order to keep them busy". |
| tooki:
--- Quote from: arcitech on October 30, 2022, 02:39:03 pm --- --- Quote from: Fungus on October 30, 2022, 01:44:43 pm --- --- End quote --- One memorable lesson I learned working in aerospace was around alumin(i)um oxidation -- it is certainly worth caring about in a variety of mission critical scenarios, such as those involving various altitude/temperature extremes, and likely also high salinity environments. Sure, it doesn't "rust" in the commonfolk sense of the term, but the mechE cautioning me as I cut holes into a vehicle of my own as I installed some electronics gear made it very clear to me (and I trusted him enough to feel like I didn't need to fact check): Al does in fact rust. It may not look like the popular definition of rust, and it may not spread like that sort of rust either, but apparently it's enough of a concern that, for some applications, any opportunity for (ongoing, not immediate) oxidation of Al warrants countermeasures. --- End quote --- Well… no. Rust specifically and exclusively means iron oxide, and only iron can oxidize to iron oxide. But aluminum does oxidize. (In other words: rusting is not a synonym for oxidation, it’s a very specific oxidation.) |
| james_s:
As I recall, aluminum oxidizes more readily than iron. The difference is that aluminum oxide mostly stays on and provides a protective coating. |
| jfiresto:
--- Quote from: Fungus on October 30, 2022, 01:44:43 pm ---... I wouldn't have thought that aluminum needed any painting. It doesn't rust and it already comes in battleship grey color.... --- End quote --- It depends on the alloy. The original Duralumin (series 2000) aluminum used by Count Ferdinand von Zeppelin, for example, contains copper, and often needs an outer cladding to protect it against corrosion. Attached is some aluminum 2014 that has been turning brown just sitting on the shelf. |
| tooki:
--- Quote from: james_s on October 30, 2022, 05:33:49 pm ---As I recall, aluminum oxidizes more readily than iron. The difference is that aluminum oxide mostly stays on and provides a protective coating. --- End quote --- Yep. It passivates precisely because it’s so reactive. The oxide is hard, and above all isn’t larger than the metal it consumed. (That’s the problem with rusting: rust is physically larger than the iron, so it necessarily starts flaking off, exposing more bare metal…) |
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