Copy Cad - Yellow Chromate does not stay on

[charlton]

Hello,

Yesterday was my first time plating and I am pleased to say that the Zinc plating went remarkably well. I was able to get VERY SHINY, almost chrome looking parts right off the bat and I would say that I was NOT very precise in the setting up of the tank etc. I just followed the procedures with what I thought was "reasonable" care.

It is worth noting that the first item took nearly an hour to plate...as if the solution had to "condition" itself for that first item. After that, plateing was MUCH faster...until the pH went too low. Now it seems it won't start plating again. So I have to wait on Ammonium Hydroxide to arrive to raise the pH.

At first my heater thermostat would not work and it heated my solution to 165 F but after tapping the sensor a bit, now it seems to be working.

A hint... I bought a laser thermometer from Harbor Freight Tools and so I can just point it at several location IN and on the outside of the tank to get an idea of the actual solution temperature.

Anyway, I used brightner and as I said the parts look like chrome... Amazing. However, I could not get the Yellow chromate to stick to these parts. It would come off in flakes and allthough "some" of the part is yellow, the part is basically very splotchy looking...part dingy chrome looking and part yellow chromate, very uneven.

I read that you should NOT use brightner if you're going to use a Chromate and I will try that after getting the pH back up.

My question is.... I see parts from Yamaha that have been Yellow Chromated and they are nice and shiny. If I can't use Zinc brightner with chromates, will the chromate "brighten" the part or are you condemned to DULL finished parts if you want a chromate applied?

Thanks

[seanc]

Charlton:

I read that you should NOT use brightner if you're going to use a Chromate

I haven't tried a real chromate w/ the brightener (plan to soon), but I can confirm that the brightener is NOT COMPATIBLE w/ the "Zinc blackener", which is an "oxide" conversion:

Blackener photos

If I can't use Zinc brightner with chromates, will the chromate "brighten" the part?

That depends on the chromate. Some impart their own brightness characteristics, while others don't (essentially remaining "neutral" to the original zinc).

Caswells yellow chromate does brighten to it's own degree. Here's a sample piece done w/out brightener:



A larger image here.

The final "brightness" of the part also depends on the pre-plate mechanical finish. A polished part will come out quite a bit brighter than a bead blasted part.

And finally, and acid bright dip makes a difference. And here, 1% nitric acid is the cats meow.

Initially I had been using muriatic, then sulphuric acid bright dips, but noted that most commercial operations used nitric. Nitric acid is very difficult to come by, but I finally got some, after 6+ months of trying.

The difference between nitric and other acid bright dips is like night and day!

Sean