Caswell Plating

[jfa.series1]

The commercial plating shop I dealt with said that anything that flexes should be baked: springs (duh), OE-style hose clamps, split ring washers, ... you get the idea.

[hr369]

I've heard some people baked too long and/or too hot and it screwed up the finish.

Edited July 25, 2016 by hr369

[Patcon]

Thanks Jim

I may separate plating batches into groups that need baking and groups that don't. I knew split washers and Belleville washers would crack. I was more worried about suspension bolts...I hadn't thought about clamps

Edited July 25, 2016 by Patcon

[Namerow]

We had a short but lively discussion about electroplating at Z-Fest yesterday.  I've now received my shipment from Caswell and I'm getting ready for what I hope will be my final (and successful) attempt.  I'm pulling my notes together before getting started.  Thought you might be interested in what I've learned about three topics that don't seem to be well understood:  chromate dips, acid pickling, and hydrogen embrittlement:

 

Chromate Dips

• Aka ‘chromate conversion’...
• The effect is called ‘passivation’
• The purpose is to create corrosion resistance for the underlying metal surface. The zinc from electroplating is intended to provide corrosion resistance for the underlying steel part.  However, the chromate is applied to provide corrosion resistance for the zinc (which is susceptible to tarnishing and becoming dull over time).
• ‘Passivation’ involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material. The technique involves the application of a light coat of a protective material (such as a metal oxide) to create a shell against corrosion. Passivation strengthens and preserves the appearance of a metallic surface (like zinc).
• The tarnishing of metallic surfaces is a natural form of passivation, called ‘corrosion coating’...
• When exposed to air, many metals naturally form a hard, relatively inert surface (e.g. silver ‘tarnish’).  Corrosion coating (tarnishing) reduces the rate of corrosion of the underlying metallic surface.  The thin, hard and relatively inert outer shell of corrosion inhibits deeper corrosion. 
• The protective effect varies, depending on the kind of base metal and the nature of the surrounding environment. At room temperature, the protective effect is notable for aluminium, chromium, zinc, titanium, and silicon. 
• When corrosion coating (aka tarnishing) occurs, the inert surface layer -- termed the ‘native oxide layer’ -- is usually an oxide or a nitride.  For aluminum, even after several years, it will have attained a thickness of only about 50 Å.

Pickling

• Pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust, or scale from ferrous metals, copper, precious metals and aluminum alloys. A solution called ‘pickle liquor’, which contains strong acids, is used to remove the surface impurities. It is commonly used to de-scale or clean steel in various steelmaking processes.
• The primary acid used is hydrochloric acid, although sulfuric acid was previously more common. Hydrochloric acid is more expensive than sulfuric acid, but it pickles much faster while minimizing base metal loss.

Hydrogen Embrittlement

• Hydrogen embrittlement becomes a problem for the pickling of some steel alloys and high-carbon steels. The hydrogen from the acid reacts with the surface and makes it brittle, leading to cracks if flexed…
• Carbon steels, with an alloy content less than or equal to 6%, are not very susceptible. Either hydrochloric acid or sulfuric acid may be used.
• Steels with an alloy content greater than 6% must be pickled in two steps and acids other than the usual sulphuric or hydrochloric are used.  Substitute acids include phosphoric, nitric, and hydrofluoric acid.
• Nickel-chrome steels (which offer rust- and acid-resistance) are pickled in a bath of hydrochloric and nitric acid.

It appears that some plating shops err on the conservative side on the matter of hydrogen embrittlement, recommending that any steel part that has been plated be heat treated afterwards if its going to see vibration or flexing in use.

 

 

 

 

 

 

 

Edited August 7, 2016 by Namerow
extra bullet

[Patcon]

What did you get in from Caswell?

[Namerow]

43 minutes ago, Patcon said:

What did you get in from Caswell?

Just the basics:  Electrolyte, brightener, blue chromate and yellow chromate.  Only enough for a 1.5-gallon tank, but these cost close to Cdn $200 and that's about all I'm prepared to spend on this adventure.

I still need to buy several small plastic pails for distilled water dipping.  I've read some comments about not sharing the distilled water bath from one step to another, so I'm going to use separate baths for each step along the way.  I'm also going to buy a squeeze dispenser that I'll use after each water bath, just to make sure that the part isn't carrying any residue from the bath into the next step (Caswell says to rinse the part in fresh cold water).  I'll get at this next weekend, while I've still got the use of Grannyknot's controllable amp/volt power supply.

I may have some questions for you during the week as I get closer to being ready to start..

[Patcon]

I will help any way I can. I am just using a spray bottle between steps because I figured dipping would contaminate fairly quickly. I haven't had any real issues yet but I also haven't done a lot of plating yet. Over time that might end up being a problem for me...

[Patcon]

13 minutes ago, Namerow said:

but these cost close to Cdn $200 and that's about all I'm prepared to spend on this adventure.

I understand, this can get expensive if you want to run larger tanks...

This is what I plated yesterday. Got good results although that may not be apparent in this picture. I would set it up and go check on the golf match or the Olympics. Plated everything for 30 minutes @ 0.14 amps / in

Blue chromate for 60 secs and yellow @ 35 seconds. I rinse it with the spray bottle between chromates and shake them off. I haven't used heat to dry them yet. Let them air dry overnight. The yellow chromate won't scratch off any more since I am going straight to yellow from blue after rinsing...

The finished color is very close to the professional stuff I have had plated 

 

[Namerow]

12 hours ago, Patcon said:

I will help any way I can. I am just using a spray bottle between steps because I figured dipping would contaminate fairly quickly. I haven't had any real issues yet but I also haven't done a lot of plating yet. Over time that might end up being a problem for me...

The consensus at Z-Fest was that the best route to plating success might be for us to send all of our parts to you!

I have a lot of questions (apologies if you've covered some of this earlier)

1. How would you describe the nozzle setting you're using to spray your rinse water after the yellow chromating step: 'mist'?  'jet'?  Or somewhere in between?
    
2. Are you heating your electrolyte bath?  What temp?
    
3. Are you heating your chromate dip(s)?  What temp?
    
4. Are you using a bubble-stream agitator in your electrolyte bath?
    
5. What acid concentration are you using for the pickling step?
    
6. Have you been using the Caswell brightener in your electrolyte bath?  Any signs detected yet that it may need refreshing?
    
7. Have you been taking any special steps when plating parts that would be susceptible to 'corner' effects?
    
8. What are the approx. dimensions of the wet part of your electrolyte bath? (I'm assuming your using a pail, so that would mean diameter and depth of fluid volume)
    
9. What is the layout and approx. total wet surface area of your zinc anode plate(s)? (I'm assuming that only one surface would come into play, so a single plate with wet surface measuring 4" x 6" would equal 24 sq.in. rather than 48 sq.in.).  I'm trying to get an idea of the ratio of anode surface are to electrolyte 'wall' area, as well as how you've placed your anodes.
    
10. Are you taking any special measures to clean or polish your anode plates between plating sessions?
     
11. Are you using a metal wire wheel or a fibre wheel to dress your parts before final cleaning?
     
12. If your cleaning process involves a solvent, what solvent are you using?
     
13. Are you taking any kind of de-rusting measures other than media blasting and wire/fibre wheel?  (e.g. chemical/'Evapo-Rust, or electrochemical)
     
14. When you've determined the amps setting you need for a given batch of parts, do you: 1) simply adjust the power supply setting up to this level and then connect to the part, or; 2) perform '1' as a starting point only, followed by using the read-out from an ammeter hooked into the circuit to do the final setting? 
    
    (In other words, you've said earlier that the amps need to be set at the power supply in a no-load condition, but it would seem to me that the actual current flowing will change after a load -- i.e. the part and the bath -- is applied.)
     
15. Looking at the overall process, when is the last time you actually touch a part with your hands?  (I'm guessing that it's when you hook up the wire that will be used to suspend the part in the various baths and dips).

[Patcon]

12 hours ago, Namerow said:

How would you describe the nozzle setting you're using to spray your rinse water after the yellow chromating step: 'mist'?  'jet'?  Or somewhere in between?

I am using a spray bottle from Depot. I keep the spray broad or it will wash off the chromate. I try not to spray them too hard or too directly...

12 hours ago, Namerow said:

Are you heating your electrolyte bath?  What temp?

Yes, the plating bath is 110-115dF

12 hours ago, Namerow said:

Are you heating your chromate dip(s)?  What temp?

I did at first, but lately they are at room temperature probably about 80dF

12 hours ago, Namerow said:

Are you using a bubble-stream agitator in your electrolyte bath?

I am using a cheap aquarium pump from Harbor Freight. Moves the liquid around but no bubbles

12 hours ago, Namerow said:

What acid concentration are you using for the pickling step?

I am using some Muriatic from Depot at about 3 water : 1 acid

12 hours ago, Namerow said:

Have you been using the Caswell brightener in your electrolyte bath?  Any signs detected yet that it may need refreshing?

I have been. I add a little every time I plate. I am unsure if it helps or not. I don't ever get bright plate like some people do..

12 hours ago, Namerow said:

Have you been taking any special steps when plating parts that would be susceptible to 'corner' effects?

Not yet... I haven't had any parts come out in a way where I needed to do more...

12 hours ago, Namerow said:

What are the approx. dimensions of the wet part of your electrolyte bath? (I'm assuming your using a pail, so that would mean diameter and depth of fluid volume)

5 gallon bucket with about 3 gallons of fluid. I had 1.5 gallons but upped it to make it easier to run larger parts or longer strings of parts... 

12 hours ago, Namerow said:

What is the layout and approx. total wet surface area of your zinc anode plate(s)? (I'm assuming that only one surface would come into play, so a single plate with wet surface measuring 4" x 6" would equal 24 sq.in. rather than 48 sq.in.).  I'm trying to get an idea of the ratio of anode surface are to electrolyte 'wall' area, as well as how you've placed your anodes.

I am running 2 of Caswell's plates, 4x8 on opposing sides of the tank

12 hours ago, Namerow said:

Are you taking any special measures to clean or polish your anode plates between plating sessions?

Nope. They are dark when they go in and almost black when they come out. I rinse them when I'm done with the spray bottle and black water rinses off. They seem to plate ok, so I haven't worried about it

12 hours ago, Namerow said:

Are you using a metal wire wheel or a fibre wheel to dress your parts before final cleaning?

I am using a steel wire wheel I bought at Harbor freight. Be careful a light touch is needed to polish and not cut up the part

12 hours ago, Namerow said:

If your cleaning process involves a solvent, what solvent are you using?

Sometimes I use my parts washer before I bead blast. Stinky solvent based cleaner. SP degreaser in a crock pot before the "pickle"

12 hours ago, Namerow said:

Are you taking any kind of de-rusting measures other than media blasting and wire/fibre wheel?  (e.g. chemical/'Evapo-Rust, or electrochemical)

I haven't done anything yet that bead blasting didn't handle. I would be comfortable using something if I had a situation that required it...

12 hours ago, Namerow said:

When you've determined the amps setting you need for a given batch of parts, do you: 1) simply adjust the power supply setting up to this level and then connect to the part, or; 2) perform '1' as a starting point only, followed by using the read-out from an ammeter hooked into the circuit to do the final setting? 

(In other words, you've said earlier that the amps need to be set at the power supply in a no-load condition, but it would seem to me that the actual current flowing will change after a load -- i.e. the part and the bath -- is applied.)

My power supply calls for a short circuit to set initial settings. After connecting the string I adjust as necessary. When I put in a new string, I adjust up or down as needed for the required amperage for that particular string

 

12 hours ago, Namerow said:

Looking at the overall process, when is the last time you actually touch a part with your hands?  (I'm guessing that it's when you hook up the wire that will be used to suspend the part in the various baths and dips).

That is correct. I actually adjusted a part the other day before plating or maybe after but before color. It left my finder print on the part...

Edited August 9, 2016 by Patcon

[Namerow]

Thanks, Patcon.  This is really helpful.  Success with this process seems to be really dependent on uber-cleanliness and getting all the details correct (hence the long list of detail-y questions ).  I just made a sweep of the Dollar Store yesterday after work to pick up a new set of virgin pans, pails, buckets, and spray bottles.  I'm going to create a fresh acid bath and bust out a brand-new wire wheel, too.  Taking no chances!

[newtonhubcap]

jfa.series1 mentioned a commercial playing shop? Do you remember the name of the shop?

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