Amps vs. Colts w.5 amp Rectifier

[BDForgan]

Hey everyone
I got my tanks up an running and I'll post my first pics that were a total success on my first runs. As I've started some additional runs, I've made a couple of silly mistakes. The first was to accidently dip the middle part of 3 hanging on my tank bar partially back into the degreaser tank from the oxidizer tank while spray rinsing with distilled water (I wasn't sure if i did, but I continued on to the ano tank/dye and sealant. No dye took to the part where I accidently dipped it into the degreaser tank. I pulled out the ano stripper that came with Caswell's kit and it worked perfectly. Reran the part through all tanks again and everything came out perfectly.

The next problem I had was an akward shapped part that I hooked up to 2 long aluminum wires running through two clean holes on each end of the part. I folded over the middle of each wire about 3-5 times to form a tight/squished kind of coil and I pulled this through the part hole so the squished coil would jam in the hole tightly – so I have 2 holes with with the wire coming out both sides of the each hole with 4 wires total running up to my tank bar. I had 25 sq. in of surface area, ran the 720 calc with 1 mil thickness, 6 amps CD, which said to set the current at 1.17 amps for 120 min with a peak Vdc at 15.

About 1 hour into the ano tank, I noticed the volts on the rectifier jump up to 29/30 volts. I read that you set the current you want on the rectifer and the volts take care of itself to maintain the amps set. When I pulled the part out of the tank after 2 hours, the part was no longer handing on the aluminum wires – they burned or dissolved away and the part fell to the bottom of the tank.

1. What happen?
2. Does it matter how many wires you have running from the tank bar to your part? I had 4 so I could control at what angle the part sat in the bath. I have recessed areas in the part that I thought would trap air/bubbles from the fish tank pump/aeriator.....
3. I could have cut 2 sets of wires that came out the same side of the part away and hung the part with just 2 wires that was jammed into each hole. Are 2 sets of wires OK (4 being way to many) or should you always only have one wire going to each part only?

Thanks
Bruce

[BDForgan]

Title: Amps vs. Volts – not Colts. How can I fix the spelling error in the subtitle
Bruce

[sswee]

You can't have too many wires to the part. You can have too small of a wire to carry the current. The jump in voltage meant you lost connection. I've had bad connections arc and spark in the tank. Should need just a better electrical connection to fix.
SS

[BDForgan]

ah ha! That must be it. The wire I'm using must must be too thin. All my other parts were a lot smaller than this part I'm having trouble with. The total surface area of the small sucessfully ano'd parts were around 12 to 20 sq. in. The big part is around 35 sq. in. I've tried to ano it twice and both times the wires burned up at the acid bath surface and the part fell to the bottom of the tank. The connections were good because the surface did anodize, but there were splotches or areas that anodized inconsistantly where the part was touching the bottom of the tank.

I'm using 18 gauge aluminum picture hanging wire. I need to try to find some thicker aluminum wire or the titanium wire.

Thanks Sswee. I'll try it again.

Bruce

[luminous]

18G is pretty small. I'd definitely go up a size or 2.
I've been using mostly .062" (almost 14G) MIG wire with no problems at all.
I picked up a 6 lb spool at a surplus yard for $12. There's probably 1500' or so on a spool that size.

The alloy is unknown, but it's fairly hard and springy, has a very smooth shiny surface and anodizes nicely. If you bend it too tight it'll crack.
It also welds nicely with my new capacitive discharge welder.

That little bit of wire just above the surface of the acid bath has the hardest time. It gets the full corrosive action of fumes and acid being sloshed on it without the protective benefits of being submerged in the acid where it can "see" the cathode and get a protective anodized coating built up to protect it.

You want to make sure the wire is sized large enough that it can afford to get a small amount eaten away and still survive, plus be large enough that the current flowing through it DOES NOT CAUSE ANY RESISTIVE HEATING.
The warmer the wire is, the faster the acid will react and eat it up. Even a few degrees greatly increases the speed of destruction

That bit just above the surface of the acid gets eaten fastest. As it gets eaten and the diameter gets smaller it's resistance in that spot increases, which causes localized heating. That heat increases the speed that the acid eats it, which causes it to get thinner faster and the resistance to increase faster which causes it to heat more...
It's a vicious circle that ends when your part hits the bottom of the tank.

Once the wire has entered the surface of the tank, it is both cooled by the acid bath, and quickly protected by an anodized coating. It's that bit just above the surface that's a bitch. Keep it fat and keep it cool...


steve