Sunday, August 7, 2011

Aluminum animus

Bronze has been around, well at least since the start of the bronze age, about 3000 BCE. As a matter of fact, the first use of metals starts with gold around 6000 BCE, and by the time Jesus appears, there are only seven known metals in the world. Their appearance in history starts with gold, then copper, silver, lead, tin, iron, and mercury. Aluminum however was first made in a crude form in 1825, and really wasn't a viable commercial metal until the late 1800's. It's a marvelous material when used in the right place for the right reasons. But I would opine that dash panels are not a good long term use for this material, especially when exposed to the salt water environment. 

In the real world, or at least in my version of it, I know why it's used, and that's because you can make it pretty, much to the delight of the marketing departments. From this installers viewpoint, the stuff is a real pain in the ass to deal with.

















So let me illustrate some of the downfalls of dealing with this dash panel material, starting with the fact that it's difficult to cut, and by that I mean larger tools are needed, and a lot more care is required to not screw it up. In most cases, a jig saw is the only pragmatic option. The problem is that the jigsaw is bulky, and it's not always possible to get it to go where you need it to on a busy dash. My second issue with the jigsaw is the inevitable vibration that will occur, and it appears that it's possible to have the vibration damage dash instruments, at least I have been accused of having this happen. This is the whatever worked, before you did the work, and I must be Abraham Lincoln drill.

Next is the mess. A zillion small electrically conductive sharp little chips inside and out, that go everywhere on a breezy day. Vacuum cleaner, brushes, rags, hoses, shaking the stuff out of wiring harness, and pulling the jagged bits of the stuff out of your knees on a bad day. It's Florida you know, and this means copious sweat, and shorts eleven months out of a year. We get one week of fall, one week of spring, and two weeks of winter. 
















So here's the real problem with the material. It is near the very top of the list of least noble metals, making it very conducive to galvanic corrosion, and it's rare to find an older aluminum dash panel that isn't suffering from "Bubbleitis". This is my made up word for paint being lifted off the surface of aluminum by dissimilar metal galvanic corrosion.

Now contrary to what you may think, aluminum does not typically corrode in a saltwater, although the presence of saltwater, can exacerbate, and speed up galvanic corrosion. Almost all of the bubbling you see on aluminum is galvanic in nature. But, pitting, which you can often see on aluminum in areas like windshield frames is also galvanic in nature, but is not induced directly by dissimilar metals. A small flaw, like a scratch becomes a small anode surrounded by the rest of the material acting as the cathode. This form of corrosion is subject to some dispute, and it was making my head hurt while reading about the electomigration of
anions into the pit.

In the end, there are two real issues that cause problems with these panels. The first is the galvanic corrosion damage that comes from the metals that are attached to the panels such as gauges, key switches, and stainless steel screws. The second problem is the flaws in the finishing, and painting of aluminum panels. A typical process might read something like this. Alkaline degreasing, rinse, caustic etch, rinse, nitric acid desumt, rinse, yellow chromate, rinse, rinse in deionized water, and dry at 70 degrees C, and then the paint.

So you could hope the manufacturer did all of this stuff, or were the panels manufactured by the lowest bidder, hoping the panels would last slightly longer than the warranty period? 
















Aluminum truly is a marvelous material with a terrific weight to strength ratio, for your mast yes, for your dash panel, I think not, unless you just can't live without the blue metal flake paint finish on it.  Besides, it's just a real pain in the ass to work with in situ.

















A short history of metals.
Wikipedia on aluminum alloys

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