Copy Cad Surface Issues

[autigers]

New to copy cad plating.

My methods are as follows:
1) Remove rust and grease (usually with evaporust).
2) Rinse in DI water
3) Use brass wheel to make "shiny"
4) Put in diluted muriatic acid until fizzling stops
5) Rinse in DI Water
6) Degrease in diluted simple green
7) Rinse in DI water
Plate (w/ brightener added).
9) Rinse in DI water
10) Dip in blue chromate for approx. 15 seconds
11) Dry in oven.

Been experimenting with various parts over the last month. Have focused mainly on nuts and bolts to work out the kinks. I know that you're not supposed to use brightener w/ chromate but I noticed I was getting "white rust?" on parts without it. I tried the diluted nitric acid but noticed it was eating off alot of the plating and turning the screws black in spots (so I've skipped this step).

Just tried a larger part today (a bottle opener) and noticed the following issue: parts come out "rough looking", i.e., not a smooth plated finish. Brightness seems fine just issues with the finished surface. Any thoughts?

[autigers]

Just got done plating another bottle opener with the following obervation: Prior to putting into the oven it looked pretty darn good. When it came out of the oven (170F which is as low as I can get my wife's oven) it had some rough spots (like sand specs under the plating) and also had some areas with bubbling under the plating.

I'm almost leaning towards issues with surface grease.

[KCV6]

Couple of things:

Make sure you remove all grey smut prior to plating. If the item is fizzing prior to plating this is bad as it will be depositing smut. The final acid dip before plating should only activate the surface not strip existing zinc or contaminates so there should be no visible reaction during this 30 second dip. This will be causing your rougness when reliefing (baking) as the grey smut residue causes the plate to blister when heated.

The no use of brightener is simply not true. It is a personal preferance thing by different people. If you want super bright chromated bits, use bright zinc plating. It just means you have to hang the parts after chromate for a day or so to get the chromate to adhere properly. I always use brightener and my bits come out great.

Only bake high tensile bits. decorative or not high stress items should be fine. To get hydrogen embrittlement to occour you really need to have had the parts in acid or plating for extended durations. Baking will also change the colour of the chromate.

Hope this helps

Cheers Mark

[autigers]

I know of smut you're talking about. When it comes out of the diluted muriatic acid bath, the part seems to oxidize to a dark grey color. I've been hitting it with the brass brush when it does this.

More to the point, however, if I understand you correctly, you are saying do NOT let the part stay in the muriatic acid until it stops fizzing. Note, my short experience has shown that fizzing will occur within 30 second time frame. For example, if I just plate a piece and am not content with it, I put it back in the muriatic acid. Seemingly immediately upon putting in muriatic acid, the part begins to fiz. Or, is the process, keep in muriatic acid until fizzing stops, remove part, rinse, remove all dark grey smut with brass brush, put back in muriatic acid (should have no fizzing now), rinse and then plate?

[KCV6]

No, what I was saying was that the acid dip before plating should show no reaction. If it does then this is not a pre-plate activating dip, it is astill stripping. Any form of acid strip that causes the item to bubble will deposit more smut on the surface. So yes to the second part, always strip back to clean bare metal first. So what you should be doing (not showing all the rinse steps between each process) is as follows.

1. de-grease and strip any paint etc.
2. acid strip any old zinc and rust. If you use a wire wheel after this then re-dip to remove anything the wire wheel smears on the surface of the item. I would suggest using a scotchbrite wheel rather than a wire wheel. This step must result in a part that no loger "fizes".
3. thouroughly wash and de-grease in SP degreaser or equivalent (soak clean)
4. 30 second acid salts or muriatic dip to activate the surface. If it is still fizzing then scrub again and re-soak clean. and re-activate remembering all the rinse cycles.
straight to plating tank.

Cheers

Mark