Zinc manganese electroplating experiment

I live in the tropics and near the sea so during the wet season the humidity goes high and everything ferrous will go rusty given a chance. There is a wealth of zinc plating resources so I thought I'd try it out and today is the third attempt at plating. The recipe came from here: http://www.plateworld.com/editorial57.htm and is based on the zinc-magnesium plating recipe but with equal amounts of zinc sulphate and manganese sulphate and retaining the magnesium sulphate. I'd read that zinc-manganese plating is pretty corrosion resistant if the manganese content is the same or higher than the zinc: cecri.csircentral.net/1282/1/023-2002.pdf

Zinc apparently needs a chromate passivate ( chromate can be hexavalent) for best performance which I don't have, so for now the items will just have to be oiled. The spanner is made of mild steel and is a square drive to fit my milling machine vise, it came out of the tank a light grey colour and after a rinse with clean water, I gave it a burnish with steel wool and it came up bright.

So the procedure was:

1. Linish all surfaces with the belt grinder.
2. Work over the surface with a scotchbrite wheel on a motorised spindle.
   
3. Scrub thoroughly with soap and water.
4. Wash with dilute hydrochloric acid, this got rid of blue oxide coating from the stick welding.
5. Place in the electroplating bath and plate for about 20 minutes, constantly moving the carbon electrode around as well as the spanner to compensate for the uneven throw of the small carbon electrode and agitating the bath the whole time.
6. Rinse off in water.
7. Burnish with steel wool until bright silver.
8. Coat with oil.
9. Enjoy!!!

Electroplating tank sitting on top of the DC power supply.


Chemicals came from either the hardware store or the supermarket.


Out of the bath and rinsed off, still a light grey colour.



After the steel wool burnish and a light coat of oil.


Close up of the plating on the welded area which was heavily oxidised before the acid removed it.


Another shot of the spanner, WOOHOO!!.

 

Sounds likely for some tools I have. Thanks.

 

It's a good idea to keep detailed notes on the process, I've been trying to get a nice bright zinc only plating and have succeeded only once so far.

 

I've had good success with copper and would highly recommend getting yourself a 60$ magnetic mixer/heater - besides the convince when mixing other solutions the agitation allows faster plating with a much better surface finish. I’ve never plated with zinc (one day) but here is the bath composition outline in my “Electroplating Bible”

zinc sulfate - 32-48 oz/gal
Ammonium chloride - 2-4 oz/gal
Aluminum sulfate - 4 oz/gal

ph range 3.5-4.2
Temperature - 75-85f

*Graham (electroplating engineering handbook 3rd)