help getting coverage with irregular part

[R.B.]

I am having problems with a particular part when I am using my old version copy cad set-up. This is a throttle shaft for a carburetor, and also a picture of a typical successful plating job, which is a fuel inlet nut. So, here is what I am doing... FIrst I am electroplating the part, with a 75 degree solution, and .1 amps / sq inch (with 3amp caswell power supply), plating for about 5-6 minutes or so. Then I dip it in a (non-caswell) acid salt bath for 2 seconds, then rinse, then into a (non-caswell) yellow chromate for 30 seconds with vigorous movement, then into rinse tank, then blow it dry.

I am suspecting that the problem I am having stems from the anodes not "seeing" enough of the part. I have two anodes, 4 inches wide x 6 inches tall (from memory on that), positioned 180 degrees apart. Maybe I need to get more anodes and position them 360 degrees around the part? And from the bottom too?

I included one picture of how I run the wire to hang the part from the copper bar at the top of the tank. I am using really small wire, but it works fine for anything else, just having problems with the irregular shaped stuff.

I am all ears to suggestions. This is the older copy cad kit, and it is a 3 gallon pail size.

[R.B.]

here are a couple of other shots. They are quite small after getting down to the 97Kb the forum requires, so I can post them on my website if anyone needs more detailed look.

[R.B.]

and here is the shot of the fuel inlet. This is the typical success I have had with the whole plating deal.... after I bought a good power supply, and some great pointers from SEANC on this forum that is.

thanks for looking, and helping,

rb

[seanc]

R.B.

I'm glad to see you're making progress! The color looks great.

As you suspected, you are indeed getting "anode shadow". Electricity always takes the path of least resistance, so the majority of plating takes place on the surfaces closest to the anodes, and not on "shadowed" areas.

However, this part should still plate fairly well:

1. 5-6 minutes is not enough time. At .1 A/sq-in, the original formula takes about 40 minutes to build up a .001" plate thickness. Leave it go for 30-40 minutes. The shadowed areas will then have time to plate, just thinner than the outer areas.
2. Turn your current down to minimum. Again, at higher currents, more of it will go to the closest parts. At lower currents, it will spread out more. Try .075-.080 A/sq-in.
3. Rotate your parts, change the positioning, while plating, so the "shadow" changes position.

Watch the shadowed areas when you do the acid dip. If they brighten up just like the outer areas, then they have plated, and should chromate well.

If after all this, you're still getting shadow, then you'll have to use more (auxiliary) anode. Thin strips shaped to fit close to the shadowed areas.

Sean

[R.B.]

Thanks seanc,

as always, great advice.

I do not know where I got my 5-6 minute dip time, I will do as you suggest and lengthen it out. I REALLY need to get more tanks because at 40 minutes per batch, it is going to take FOREVER to do it the way I have been. It is staggering the amount of parts that a quadrajet carburetor has when FULLY stripped!

I will report back after some experimenting tomorrow.

I am glad you mentioned the 'brightening" after the acid dip. As you may remember, I am using a non-caswell acid salt dip, and I was wondering it that was something unique to that chemical. It actually is a blessing sometimes, as with a pure rookie like me, sometimes I get a burned edge or two and the acid dip makes it more presentable

rb

[R.B.]

Oh, and I forgot to ask you, did you once mention a low cost alternative to zinc anodes... maybe it was something from home depot, flashing or something? thanks,
rb

[seanc]

R.B.

I REALLY need to get more tanks because at 40 minutes per batch, it is going to take FOREVER to do it the way I have been.

It doesn't always HAVE to be that long. It all depends on how thick a plate you want, and that is purely current & time dependent.

In this case w/shadowed areas, longer times will be helpful.

Commercial fasteners have very thin plate, .0002-.0004 or so. That's what's nice about DIY, you can plate as thick as you want, and end up w/a part that's better than new!

I am using a non-caswell acid salt dip, and I was wondering it that was something unique to that chemical.

I forgot to ask about that yesterday, but am curious. What exactly are you using? "acid salt" can be any one of many different concoctions. And what concentration (% wise)?

All you need is a pure acid, appropriately diluted. Nitric is best, but difficult & expensive to obtain. Muriatic is second best, available at any local hardware store as "concrete cleaner" (muriatic is pre-diluted hydrochloric acid, about 30% solution). Only sulphuric should be used before black chromate.

OTOH, yellow chromate already has a significant acid content, and is "self-brightening". You don't really need a pre-dip.

Sean

[R.B.]

update!

For the throttle shafts, I did as you suggested, and dailed the amps way back, then left it in there for abour 50 minutes, while moving the anodes 3 times. That left me with a very nicely plated part. I chromated it and it turned out super. THANK YOU!

I have to ask you something that I have seen you mention before. With my copy cad set-up... It seems like when I don't have brightener in there, everything turns out really dark, and does not chromate well at all. I noticed you mentioned that you should never use brightener if chromating the part... well it must be something with the yellow chromate that I am using, but it does not rub off after. in fact, it really stays put. it must be something in the particular chomate I am using, because you are THE MAN when it comes to the caswell stuff. Anyways, I thought I should mention that because using brightener is the ONLY way my parts turn out worth a darn.

Oh, and the acid salts and yellow chromate are the ones I emailed you the PDF file of, back in October or so.

When I take the part out of the copy cad, then dip it for about 2 - 8 seconds in the acid salts, the part really shines up, then into the chromate. If I just chromate out of the copy cad, it does not brighten up the same.

Man, I never wanted to be a plater, just wanted to shine up the stuff I sell, but it really depends on alot of trial and error, that is FOR SURE!!

rb