Caswell Plating

[Patcon]

I did use all the blue chromate when I mixed it up. I hate it that Caswell doesn't send as much blue as the yellow. When I used the blue before the pieces brightened up almost immediately, After adding water, even after 2 minutes they don't brighten up like that...that's why I wanted to check Ph levels...

I ordered a Ph meter from amazon for $20...

[Patcon]

As an aside I plated some hardware yesterday. The blue didn't brighten it the way it should but aside from that I baked this batch because it goes on the skid steer I'm rebuilding. The baking seems to darken them up even more and they seem to have a brown tone too...

[240260280z]

I read that a dip in nitric acid helps to brighten in one of the links earlier in this post.

[Patcon]

I suspect both chromate dips are Nitric base, that's why I want to check the Ph of the tanks

[motorman7]

I have never considered the blue chromate as a brightener.  The blue helps with the 'rainbow' effects and sets up a good base for the yellow.  Usually my bolts come out dark or brown when I leave them in the yellow for too long.  I have heard what Blue mentioned above, nitric acid as a brightener, but I have never used it.

[240260280z]

Sorry the internet died

 

I dug up the old thread:  http://www.britishcarforum.com/bcf/archive/index.php/t-8760.html

 

Pictures are gone but the Nitric acid sure made the parts look mighty purdy. 

 

 

Here is the good stuff from the thread (in fact read the full thread!):

 

John Loftus

11-23-2005, 11:58 AM

I use the bucket that came with the kit and it works fine although the rectangular tank would probably be more efficient use of space. I use a small aquarium air pump (I bought the one from Caswell when ording additional supplies and it was only $15). Don't use an air stone on the line .. the large bubbles from the air line work better to stir up the mixture. The line wants to float so I wired a nut to the end to drop it down to the bottom of the tank.

I have changed my methods just last week. I learned from Sean that chromate conversions add to the durability of the zinc finish so I purchased the clear (blue) chromate dip from Caswell. I also obtained some Nitric acid that has been diluted down to 1% solution. Now my process is:

1. Clean, prep parts by bead blast, tumbling or wirewheel.

2. remove all traces of old zinc with muriatic acid (diluted 4 parts of water, 1 part of muriatic). Leave parts in until bubbling stops.

3. rinse parts with water and then use fine brass wirewheel on grinder to shine parts, clean threads, etc.

4. degrease parts using diluted (about 20%) purple industrial cleaner (from Home depot) or Simple green with brush. Rinse with water

5. Wire parts and zinc plate.

6. Dip parts in distilled water bucket

7. Dip parts in Nitric acid for 1 to 5 seconds (this brightens the parts and removes the brown tint of zinc plate solution)

8. dip parts in distilled water bucket

9 dip parts in blue chromate bucket for 15 to 30 seconds.

10. unwire the parts and put them in shop oven 140 degrees F for 15 minutes or so to dry the parts.

The parts now look store bought and the zinc is far more protected (some of my early experiments were losing their shine quickly because the zinc was exposed to the elements)

http://www.loftusdesign.net/zinc11_23.jpg

 

[Patcon]

Thanks Blue

I read through that. I don't know if I can acquire Nitric locally. It has become fairly highly regulated in the last few years due to some of it's alternative uses...

[Namerow]

30 minutes ago, Blue said:

this brightens the parts and removes the brown tint of zinc plate solution

The only time I've seen parts come out 'brown' from the electrolyte bath was when I when I realized that flash rust had set up before they went in.  Zinc is grey.  I'm not sure how it can become brown.  Depending on how good a job I did at cleaning the parts and setting the amps and adding the brightener, my parts come out of the electrolyte anywhere from dull grey (adequate job) to shiny grey (great job) to grey-black-with-black-flakes-attached (crappy job).

Re chromates & pH levels:  I'm not a chemist, but it's my sense that neither of the chromates works by way of acidity.  The brightening effect that I've observed (in my admittedly brief experience with all of this) was achieved by virtue of the Caswell 'brightener' liquid that I added to electrolyte before I started a new plating cycle.  It really does make a difference.  More so, I think, than polishing the actual part  before starting to plate.  In fact, I didn't even use the wire wheel on the last couple of parts that I plated (they were just glass-bead-blasted) and they seemed to come out pretty good.  The Caswell brightener is supposed to 'brighten' by way of making the zinc deposit/plate out on the part's surface in a smaller particle size.  I'm not sure how a dip in nitric acid after plating would brighten a dull zinc surface.  But -- again -- I'm not a chemist.  Maybe someone else can chime in here.  

While I prefer logic and science, there seems to be a dose of witchcraft (or maybe 'which-craft' would be more accurate?) involved in DIY plating.

[240260280z]

1 hour ago, Patcon said:

Thanks Blue

I read through that. I don't know if I can acquire Nitric locally. It has become fairly highly regulated in the last few years due to some of it's alternative uses...

I had the same problem however when I said I wanted 1% they said no problem   I have  4 gallons of the stuff... minimum order. I think vinegar is more dangerous!

[240260280z]

old brightener trick was sugar!

http://thefactoryfiveforum.com/showthread.php?14392-DIY-Zinc-Plating-for-Donor-Nuts-and-Bolts

"5) Sugar from the grocery store (plain old table sugar). Sugar is the "Brightener" of the plating solution. It actually interferes with the formation of zinc crystals, causing many smaller crystals to form on the surface instead of fewer larger crystals, thereby improving a frosty looking surface to a smoother more reflective one.

[240260280z]

If you just want silver coloured zinc (like door strikers)

 

The plating solution recipe (which you can scale up or down as you like):
1 liter of vinegar (5%)
100 grams Epsom Salt
120 grams sugar
8 - 10 square inches of zinc pieces

Add the Epsom Salt and sugar to room temperature vinegar and stir until dissolved. Add the zinc pieces and leave lightly covered for 24 hours.

 

http://thefactoryfiveforum.com/attachment.php?attachmentid=29064&d=1400040203

[240260280z]

Another home brew: http://www.mgexp.com/phorum/read.php?2,2013753

 

1 bottle White vinegar as the acid base for the plating solution

5T Epsom salts (table salt creates chlorine gas - "Epsom" is magnesium sulfide) to improve conductivity

10T White table sugar (as a "brightener" )

1 drop dish soap (as a water "wetter" )

3" wide coil of zinc (from the Home Depot roofing section - used to prevent moss on roofs)

"Acid Safe" muriatic acid

Acetone (small metal or glass container with a lid)

Baking soda dissolved in a bucket of warm water (to neutralize the acid)

Battery charger or 6V power supply - one dry cell battery works just fine.

***Mix the sugar, salt and vinegar. Line a small plastic tub or pail with the zinc and make a triangular fold in the flat stock so that one end sticks up and over the side as the negative electrode connection point. I put a small piece of copper tubing across the top and bent up some copper (14g romex) wire S-hooks to hang my parts. The battery charger Positive (+)terminal goes to the zinc, and the Negative (-) goes to the copper bar or the part to be plated. When you hang the parts off the copper into the solution, it completes the circuit.

***Wire wheel all loose rust and scale and crud off the parts, clean with hot soapy water to degrease if necessary. Put part on copper hook. Dip part in acid (don't breathe it) to de-rust, then in baking soda and water to neutralize, then dry with paper towel and dip in acetone to completely degrease (denatured alcohol works too). Then let the acetone evaporate and place the part into the vinegar and salt bath by hanging on the copper bar.

***Part will plate in about 3 minutes. If you leave it in too long, it gets lumpy. Take the part out, neutralize in baking soda/water. It will appear black. Wire wheel until shiny. Then dip in acetone again to clean and re-plate. Think coats work better than thick coats. After two or three coats you can wire wheel (a soft metal wheel or brass wheel is good) to a dull shine.

As the day went on, the parts plated faster, I think because the vinegar was "polluted" with more zinc ions that it had been initially.

If you leave the parts in too long, the copper hooks start to plate the parts with copper, so again, thin coats are best.

For small parts (like screws) instead of the hooks you can wrap them with copper stranded wire to hang them.

I am now making up a copper plating bath as well. For pitted parts, you can copper plate them to fill the pits, then plate with the zinc. The zinc is shiny-er over copper than pitted steel. I also want to experiment with the amount of sugar and salts. Too much salt isn't bad - it just precipitates out and sits on the bottom of the bath. I want to try it with no sugar (you can always add more) to see what the result is.