Yellow chromate, whats the secret?

[KCV6]

Hey Tom,

The Gold Chromate is always fragile until cured, especially on bright shiney zinc surfaces. However if the zinc to be chromated is fresh from the plating tank and nice and warm, this helps.

I rinse my zinc bits from the tank in really hot tap water in a rinse bucket and then rinse off with distilled, then do a quick activate, rinse (distilled) and then straight to chromate. Even pulling the items from the chromate tank too fast can cause the chromate to pull off on and around edges. I then carefully rinse with a misting bottle over the chromate tank so as not to drag and waste chemicals. My next step is to slowly imerse in hot water for a few seconds, I then leave to air dry for a few minutes and if needed use a hot air gun to blow excess water off. This is less than 10psi, just a standard wagner paint stripping hot air gun.

Hope this helps

[kxkraze]

Tom,

I don't know if you have found a solution to your problem yet or not but I will share with you what I have found and works quite well.

1) According to the caswell employee that I spoke to, this is the place where they buy the chromate in bulk.http://www.epi.com/metal-finishes/zinc-chromates.html. Now you have instructions directly from the chemical manufacturer.

2) The best method that I found for using brightener and not getting slough is to perform a blue chromate dip for about 40 seconds followed by a yellow chromate dip for a duration up to desired color. I then double dip rinse. First tap water then distilled water. Next, I hold a hair dryer about a foot away and blow any drips away with very light air pressure. You can even just use your breath. You can use a heat gun but be careful not to exceed 150 degrees. The EPI rep. warned me that it can have negative effects. When there are no more water dropletts visible, I place the object in a toaster oven at 150 deg. F. for about an hour. This rapidly speeds up the curing process.

I don't know exactly why the blue chromate was my problem solver. My best guess is that the blue chromate has better "adhesion" characteristics when interacting with brightened zinc. It then acts as a foundation for the yellow chromate. Regardless, it works.

Regarding the darkened anodes -- mine are almost always dark and they have no ill effect on my plate.

[red911]

Thanks Mark and Kxkraze, looks like I have a lot of work to do bringing my system up to both your current specs. I'll let you know how I make out.

Tom

[kenrinc]

This is interesting. I've never had a problem with chormating any of my parts and I've been doing it for over 3 years (prior to Caswell's release of the blue stuff). Rinsing between plating and chormating is a very important step (as others have pointed out). My parts usually take about a 30min dip. The amount and look of the iridescence will not be apperent until the part has dried. For me personally I have a rack that I put the newly chromated part on and when I come back to look at them after 15 min or so in front of a small space heater they look absolutely stunning.

I would like to know the deal on the brightner msyelf. I never ran into any problems with it but I liked that really shinny look that I was constantly adding it and kept running out. Does it make sense to maybe polish the part first and then zinc plate without brightner?

Ken

[red911]

I just ordered Blue Chromate from Caswell today. Cleaned and filtered my solution. Interestingly, a old anode was at the bottom of the solution and it was about 2 inches by 2 inches. When I ran five strings of parts today, the anodes were still graying after that. I also ordered anode bandages from Caswell too.

I tried the 150 degrees F for an hour and using the paint stipper heat gun to get the water drops off the parts after Gold Chromate dipping.

Parts were better than before, but some sloughing, but not much!! Yippee!!

Here are my questions.

1. The Caswell Gold Chromate runs at 80 degrees F, do I need to heat the Blue Chromate too?

2. Agitation. How do you keep the air system at the bottom of the tank to generate aeration? Do you expoxy the air line to the bottom of the tank? I have a four gallon cylindrical bucket.

Thanks in advance, Tom

[KCV6]

Tom,

Email me and I'll send you some instructions on how my tanks are setup using garden "ridge risers" these are rigid PE tubes and fittings for microspray watering systems. Some are more rigid than others. They still tend to float a bit but not as badly and generally can be set in position.

mark.smith5@baesystems.com

Not sure with the silver pass on heating. Mine is a different setup.

Cheers

Mark

[squidix9]

Wow, I must have the touch?

I chromate a lot of my pieces and it works great. As soon as I finish the plating I spray rinse with DI and go right to dipping it. Once I have the desired color I pull the part and spary rinse with the same DI. I can handle the part immediately and it's rock solid. The only way to get it off is to use and abrasive. I have none of the issues you guys are seeing.

I''ll look at the type of chromate I have and maybe a batch number? I got it right from Caswell and have been using the same batch for years.

[KCV6]

There are different types of Chromates. I use 2 types.

Ecopas (local product) is great as it won't "slough" and is hard with in hours if warm, but it is pretty much gold coloured with none of the purple/blueish hues. It will disolve in acidic solutions very quickly even when fully cured.

Zinmax cant be touched for at least 2 days if left to air dry as it will fall off, but is tough as nails and has the nice blu/purple hues once it has cured. I air cure this for a day then bake at 150 deg C for a hour or so to harden.

In my gallery pics, the brake callipers are ecopas (45 second dip) and the recent mix of cooper S bits are Zinmax (20 second dip).

I always hot water dip for about 10 seconds straight from the chromate tank. this part cures the chromate enough to be more forgiving.

Cheers

Mark

[red911]

Update with new setup:

Yippee!! It works!!

My issue with Yellow Chromate soughing off is solved. I took the forums advice of using Blue Chromate as an intermediate step between the Copy Cad and Yellow Chomate and it works great, Plus the Blue Chromate is a wonderful product in its own right.

Here is my process with a 5 gallon Copy Cad pail system with at 25 amp recifier:

o I prepare the parts by using a 6 inch bench grinder with a fine wire wheel, or for rougher parts, I use the blasting cabinet.
o I wire the parts with brass picture frame wire to increase the conductivity of the wire. Additionally, I use a small spring for small bolts and a larger spring for bigger bolts. Also, I have bent a few wires to carry washers and bolts. Looks like a continuous "z" with about 10 or 12 places for washers and nuts.
o I use the Caswell, SP Degreaser heated to 180 degrees F in a three (3) quart crock pot. I rinse the parts on the wires for 20 seconds to get rid of the fingerprints and remaining oil.
o Then, I rinse in a 5 gallon pail with tap water for 5 seconds.
o Then, I place the parts in Muratic Acid for only 5 seconds if the parts are rust free, to etch the metal. If I cannot wire wheel very small washers or other small parts, then I will only soak those parts for a max of 20 seconds, as I have found that the Muratic Acid will turn the nice, shiny wire wheeled parts a dark color and all I want to do is etch the parts.
o Then I rinse the parts coming out of the Muriatic Acid for 20 seconds in the plain tap water pail and then follow that rinse up with a spray bottle filled with distilled water (NEW STEP).
o Heat the Copy Cad to 90 degrees F and put bandages from Caswell on the anodes (NEW STEP). Personally, I plate for six minutes per side at a very small rate with small bubbles from the nuts and bolts to be plated. I am not smart enough to measure the square inches of the parts to plate. I use the Caswell Copy Cad Brightner too. A tablespoon every four cycles of plating.
o After the 12 minutes of plating, I spray the parts with the spray bottle of distilled water (NEW STEP).
o Then I place the parts in Blue Chromate from Caswell for 20 seconds at room temperature and I get the most wonderful, deep, shiny parts from the Blue Chromate (NEW STEP).
o Then I spray the parts with distilled water (NEW STEP), and place them in Yellow Cromate for 45 seconds. The Yellow Chromate is heated to 80 degrees F.
o Then, I spray the parts with distilled water (NEW STEP).
o I hang the parts for 48 hours.
o I have not baked the parts yet, but I will do that in the next day or two.

This is my process, and I can tell you that the process has totally eliminated the sloughing issue of the Yellow Chromate and the parts (carb parts in this case) present in the yellow, red and green flowing colors that we all want!!

This is the process that will not fail you.

Good luck, Tom

[kxkraze]

Tom,

Congrats on your success and thanks for the write up!!

FYI -- I referbished a very high end golf course greens mower last year with the Caswell zinc system -- double chromate (blue then yellow) on everything. Some of the parts are carb. parts and the machine has been used all year. The zinc and chromate job has held up great!!! There are only a few parts that will need to be replated this Winter and that is because they were in high wear areas and I expected they would need replating. Even in those high wear areas, the chomate conversion coatings were removed by abrasion, but the zinc plating held up and did not expose the raw steel -- which is the ultimate goal of electroplating anyway.

Anyway, congrats on your success again.