Too much brightner?

[seanc]

Ken:

I've got a 1 ohm, 10 watt unit I can try. Seems like a small wire for such large current though.

10 watt won't be enough for many amps. In a worst case scenario, you might be dropping as much as 2-3 volts across that resistor, and passing 15 amps through it. That works out to 45 watts.

At best, it's only enough for @ 10 amps, if you can keep the voltage drop <= 1 volt.

I'm still dumbfounded on how to get a better idea of the surface areas involved.

It's a tough one isn't it! I've resigned myself to taking good measurements of all the various sides of a part, and pluggin them into a spreadsheet. That gets me close enough, but it's very time consuming.

I've used the bath to plate a plethora of smaller parts yesterday with no problems at all! Large parts are a definite learning experience for me!

Then your electrolyte is good! It's got to be a surface area calculation, anode area and/or separation, or power problem (too much or too little)!

Sean

[kenrinc]

Sean, yeah yesterday I plated a ton of smaller parts and the new solution is working great. The resistor was the ticket! Having all those anodes hooked up gave super coverage like I've never seen. That must have been my problem all along (or at least part of it). The resistor was good to about 2.2amp. It might do more but at 2.2 you could not even touch it! If I sprayed it with water the water would instantly burst into steam! I've got an old 8ohm, 50watt power resistor that I can experiment with. Can I use a "non-inductive" resistor?

Having 3 gallons is a definite advantage. It worked great. I'm going to try doing the calipers again after an acid strip of the old coating.

One thing I did run into is an issue with the chromate. Have you ever seen parts where, even after a thorough rinse out of plating bath, you chromate and the chromate will actually not cover some areas? It's almost like someone rubbed the chromate off in that area. Like it's broken or scratched off. Very weird. It is usually only in a few small spots but it bugs me.

Ken-

[seanc]

Ken:

Progress! good deal.

I've got an old 8ohm, 50watt power resistor that I can experiment with. Can I use a "non-inductive" resistor?

High resistance is too limiting, stick with 1 ohm or so. 8 ohms will drop a lot of voltage, eg. at 2 amps, you'll get 16 volts across the resistor alone (V=IxR). At 10 amps, you'd need 80 volts. Can your power supply handle high voltages? At high amps, you may not need the resistor at all.

Non-inductive is good. Any kind of power resistor will do, the wattage is what's important.

Have you ever seen parts where, even after a thorough rinse out of plating bath, you chromate and the chromate will actually not cover some areas? It's almost like someone rubbed the chromate off in that area. Like it's broken or scratched off. Very weird.

Are you using the zinc brightener? If so, you almost have to use an acid bright dip afterwards. The brightener seems to leave some sort of film on the parts, which can interfere w/conversion coatings. I have stopped using it.

Check this out: Blackener & brightener

Sean