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Don't run 10 amps through 1 18ga wire

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  • Don't run 10 amps through 1 18ga wire

    I'm new and blissfully ignorant in the anodizing world, but I've been into electronics and electricity for 30 years.

    I was anodizing a piece that's over 360 in? surface area, so I needed to push 10 amps through it. It has other parts epoxied to it, so my focus was on making sure they each got a piece of the current instead of what (to me) should have been patently obvious. (BTW the epoxy held up through the acid and temps of dye/sealant, pretty amazing)

    I got everything wired up, turned on the power, and watched. Everything looked great, so I went inside. When I came back out just a few minutes later, the power supply told me something was wrong - it was at max voltage. I cut the power, looked down, and saw that the titanium wire hooking the supply to my work had melted through a corner of my rubbermaid bin.

    You know what I was compelled to do next, no choice at all: I grabbed the wire with my fingers to verify that yes it is indeed almighty dadgum hot. I figure the only reason I didn't burn myself was that even before I chopped the power, the circuit was essentially open (as evidenced by the fact that the supply had gone to max voltage to try to maintain the current) so the wire had already cooled a significant bit.

    The solution was easy enough: run multiple wires from the supply to the work, as well as from the cathode plates back to the supply. You can sort of guesstimate that given wires of the same gauge and length, each wire will carry a relatively equal share of the load. For example, if you run 5 wires in this 10 amp situation, each carries 2 amps. In actuality it's more complex than that because of the differing resistances of the connection points & objects, but in general this is close enough to keep yourself from building a giant electric toaster.

    My advice, then, doesn't concern anodizing directly because I'm new and don't know anything yet. Rather, it's on safety. My biggest problem was getting tunnel vision on a particular aspect and forgetting the process as a whole and in particular an aspect with which I'm intimately familiar and experienced. Keep in mind that in addition to chemicals you're dealing with electricity, which doesn't in general play well with water. Never ever get between the electricity and water or that constant current supply will do its level best to turn you into a french fry.

    Before you inhale, bend over and peer into something, stick your hand in, or hit a switch, pause and think about what you're doing. Safety equipment is as much for unforseen events as it is for shrapnel and fumes you expect to encounter, so wear it even when you just know you don't need it - any inconvenience is well offset by keeping your body parts intact and in working order.

    Isn't it great when some idiot tells you how stupid he was and then has the audacity to hobble up onto his soap box? I'm lucky that I don't have a couple of grooves in my finger & thumb or that a glowing piece of wire didn't snap and fling itself against a piece of wood or flammable chemical that's probably lurking in my work area, so my only hope is that my luck can benefit you in some way.

    Now, does anyone know how I can extract that wire from the plastic bin?

  • #2
    Re: Don't run 10 amps through 1 18ga wire

    Don't feel bad. I can't tell you how many times I've connected my Fluke DMM across a car battery...with the probe plugged into the AMPS position! It's pretty exciting. Once I actually saw the meter read 120 amps. I didn't think the display was made to go that high, but it did. It's a 10A meter. The leads were sure hot, even after only about 2 seconds of contact.
    Steve Dold