PDA

View Full Version : Plating setups...what do you use?



Too_Many_Tools
06-21-2010, 11:09 PM
I am considering doing some plating...and I am wondering what I should be looking for for plating tanks, heaters and power supplies.

I would be interested in seeing what others use for plating both small and large items.

Thanks

TMT

davidh
06-22-2010, 07:57 AM
do you have the Caswell book on plating ? i have their big kit, comes with everything except battery acid and distilled water. they send 6 gal plastic buckets with clamp type covers. the book explains nearly every situation you might run into with a home shop. like using plastic plumbing pipes for long items, or only plating 1/2 the length of something and turning it around in the tank for the other half. . . . . great read, tons of info.
i plan on setting mine upyet this year. it takes space i don't have because of the chemicals involved, and i don;t want it in my machine shop area. . . .

Too_Many_Tools
06-22-2010, 04:45 PM
Thanks for the rec for Caswell...I was aware of them but haven't read their book yet...time to put it on my reading list.

One of the reasons for the original post was to learn what others use for tanks, heaters, power supplies so I can start looking for likely candidates.

I agree on keeping the plating setup SEPARATE from your machine shop.

TMT

Black_Moons
06-22-2010, 08:09 PM
for those wondering about why to keep it seperate, Consider that acid evaporates and condenses on.. everything... equals rust city.

davidh
06-22-2010, 09:25 PM
Thanks for the rec for Caswell...I was aware of them but haven't read their book yet...time to put it on my reading list.

One of the reasons for the original post was to learn what others use for tanks, heaters, power supplies so I can start looking for likely candidates.

I agree on keeping the plating setup SEPARATE from your machine shop.

TMT
like my last post, said, plastic buckets, sewer pipes, whatever is not metal. for heaters the ones that are suupplied are from fish tanks and so are the air bubblers. for a power supply, caswell goes into deep explaination about it and i ended up buying a monster from a dude on ebay for something like 1100 $$$$$. but it will handle fairlybig parts. . . . get the book. . . might even find one on ebay or amazon

AlleyCat
06-23-2010, 12:11 AM
I was in the plating business for many years and it does rust everything near the tanks. Most of my plating work was for printed circuits using two 500 gallon acid copper tanks and one 400 gallon tin-lead tank. The acid copper tank was air agitated and that put a blue film of copper sulfate on everything near the tank. We ran the rectifiers for copper at 0.75 to 1.0 volts depending on the job. The current density was 25 to 30 amps per square foot. Those rectifiers were capable of 500 amps each. The parts came out with a mirror finish if the brightner chemistry level was correct.

I closed that plant ten years ago but still do some plating on a much smaller scale and much of it is done using brush plating. It's a home made setup using a carbon rod wrapped with gauze that is dipped into a tray of plating solution. Brush plating can deposit metal pretty fast due to the high current density from the relatively small contact area of the plating brush. The carbon rod from a flashlight battery works good for a brush electrode.

One small part that I nickel plate is round so I rigged up an old drill chuck to a gear motor that slowly turns the part while the brush applies the plating. This assures an even plating thickness around the part. A carbon brush makes contact to the chuck which keeps current from flowing through the motor bearings which would ruin them.

All of my rinsing is by low flow spray nozzles for water conservation. I have no sewer connection so all rinse water flows to an evaporator tank. This tank heats the waste water to about 150 degrees F. A set of slowly rotating metal disks revolve in the heated solution which exposes it to a forced air flow through the tank. The air flow carries away the water vapor and leaves behind the waste material. This system will blow off about ten gallons per hour in the winter and a little less during the summer due to high humidity.

My brush plating rectifier is a 1 amp 12 volt DC wall wart plugged into a small variac. Another rectifier I use with a tank system is home made from a 5 kVa buck boost transformer. A variac powers the transformer and the output goes to a bridge rectifier and filter capacitor. I also use this rectifier to power up a tank of soda ash solution for rust removal. As suggested, the Caswell book and supplies are a good way to get started in plating.

gmatov
06-23-2010, 12:51 AM
TMT,

First, what are you anticipating plating? In this day and age, it probably isn't auto bumpers. If it is small items, as Alleycat says, brush plating would suit you.

He could tell you better than I, too, that your result would depend on your prep. You can't make a rough item mirrorlike if you have scratches and pits in the base metal.. You can plate and grind, and plate and grind, and eventually eliminate the dips. Dollars and solution is the cost, there.

I have a system that is self contained, about the size of a small suitcase, offset spatula to slip a woolen sleeve over for the mop, integral power supply. OLD. My intent for it is to silver plate some of my brass framed BP pistols. 6 pint containers of Silver solution, and you MUST be careful with them. Contain Cyanide. Good ventilation is a must when plating.

Alleycat,

Where do you vent your exhaust when plating? Through a water bath to capture the poisonous vapors, or what? I haven't used my outfit, not because I can't rig an exhaust to blow fumes out of the shop, but for fear that they will settle and sicken/kill my neighbors.

Cheers,

George

gwilson
06-23-2010, 07:41 AM
Lots of small jewelers have died plating with cyanide solutions in their apartments. I only use acid based solutions.

mike petree
06-23-2010, 08:17 AM
I use a small plating setup from Caswells. I had been using a stainless steel aquarium heater for the tank but now use a small hotplate. I set the tank
(a small plastic bucket) in a large metal bowl with water in it and place on the hotplate. Heats up quicker than the anemic aquarium heater and doesn't steal valuable space in the tank. The power supply is a used variable voltage/amp unit from ebay that suited the power needs for what I do. Works very well for nickel plating the small parts I make for my resto biz/hobby . Easy to set up and take down and the cost was reasonable. And yes, metal prep for plating is like prep for painting, the smoother the base surface the better the result.

Mike

Evan
06-23-2010, 09:42 AM
I use tin and silver electroless strike baths mainly for circuit boards. They are sodium cyanide based. Sodium cyanide is toxic but not in the same league as potassium cyanide. For plating silver there is no good substitute for a cyanide bath. Acid baths don't have the same adhesion or even deposition and leveling although that is not relevant for a strike bath. What does matter is that a cyanide bath doesn't rust everything in sight.

If used with a tiny amount of ordinary caution as you would any toxic chemical a sodium cyanide bath presents no unusual hazard. Don't lick your fingers or drink it and don't get it so hot so that it makes vapour. True stories of people dying from home plating baths are rare, urban legends are common.

The biggest problem with a sodium cyanide bath is disposal of the leftovers. The answer to that is to react it with sodium hydroxide (lye) to bring the pH to at least 10, then react it with bleach which decomposes both the bath and the bleach to evolve CO2 and nitrogen gas leaving behind sodium chloride. Left over bleach (sodium hypochlorite) will dissociate on it's own in a few days if left open to the air as it will oxidise the solution to leave NaCl and water.

Cyanides are very simple compounds that are easily created and destroyed.

Dr Stan
06-23-2010, 11:07 AM
All of my rinsing is by low flow spray nozzles for water conservation. I have no sewer connection so all rinse water flows to an evaporator tank. This tank heats the waste water to about 150 degrees F. A set of slowly rotating metal disks revolve in the heated solution which exposes it to a forced air flow through the tank. The air flow carries away the water vapor and leaves behind the waste material. This system will blow off about ten gallons per hour in the winter and a little less during the summer due to high humidity.

AlleyCat,

You brought up a very important issue in regard to plating, the disposal of the wastes. When I was in the Navy I was sent to the Dalic Brush Electro Plating school in Monrovia CA. Later when I was on the Gompers we simply dumped the wastes into the ocean, or even the harbor when we were in port. That of course is not acceptable, nor should it have been then (1975-77). You have described a very elegant method of waste disposal which I hope other members follow.

BTW, brush plating is very versatile. We plated many very small items and some quite large. The largest one was the commutator rings on a ship board generator which measured about 3' in diameter. We trued up the rings in place with a portable cross slide and then plated the rings with rhodium and gold. We would also plate pump and motor shaft bearing journals with nickel holding thickness within .00005" then flashing them with tin to reduce fretting after assembly. For the shafts we had a dedicated lathe that was used for nothing but plating. You can very well imagine what it looked like even though we tried to take care of the machine.

I've decided not to set up plating in my shop as I just have way too many irons in the fire and just would not use it to much degree. However I do remember a gold plated Philippine one peso coin was quite useful in getting what you wanted for a very low price. :D

Stan

AlleyCat
06-23-2010, 01:14 PM
As gmatov mentioned, surface preparation is very important in plating. If the surface is rough it will show up in the plated metal. Any sharp corners will receive more plating and may even "burn" if the plating current is too high. Recesses and holes will receive less plating. A large flat plate will build up heavy plating around the edges and corners while the center will receive the least amount of plating.

Most of my work in the past was printed circuits and were easy to do as far as plating goes. Every part was treated as a large flat part. Some parts needed special plating racks and fixtures to shield the areas where burning could occur. We made these in house and arrived at the final design by experimentation and sometimes by accident. Some of these were long running jobs so it was worth it to take the time to work out the rack design which allowed plating at the highest current density and minimum time in the tanks.

Parts with irregular shapes like some of us on this forum are machining can present problems when plating due to deep holes and recesses. This is where brush plating comes in handy. On larger jobs where a tank is used it may take special racks or chemistry. Some plating chemical suppliers have developed brightning chemicals that assist with leveling out the plated metal. Sometimes it takes a little experimenting to get hang of it but once you do the results are impressive.

The day of reckoning in the plating business was April 27, 1984 when new laws and regulations went into effect concerning plating facilities. My shop wasn't that big and we barely made it into the small shop category. The main issue was waste water flow volume. Anything over 10,000 gallons per day was considered a large operation. Other factors were taken into consideration as well such as a captive shop vs. job shops. I was considered a job shop and my waste water flow was about 9400 gallons per day.

I took a close look at everything we were doing and made changes in chemistry and rinse tanks. In the end I got the flow down to about 75 gallons of highly concentrated rinse water per day. This was batch treated with an electrowinning cell which is a special plating tank that strips most of the metal from solution by plating to stainless steel plates. After treatment that batch was transferred to a heated tank that fed a pretty large atmospheric evaporater tank.

We would run the evaporator every few days as needed and it could blow off about 60 gallons per hour of water vapor. We were allowed to use a system like this because everything was aqueous based with no solvents or volatile organic compounds (VOC). The evaporator pipe stack had a mist collector pad to catch any droplets and I would have them analyzed on occasion by a lab and we never once exceeded the regulated limit. The only thing that left the plant was nearly pure water vapor from that system.

We also had a fume scrubber that was basically a large diameter pipe full of special shaped spheres that looked like wiffle balls. A nozzle sprayed water from the top down to a bottom sump while a blower pulled chemical fumes from the bottom through the balls and out through the roof discharge. The wet wiffle balls presented a large surface area that collected any chemical mist and cleaned the air. This system evaporated quite a bit of water so it not only cleaned the air but also acted as it's own mini evaporator.

The NAFTA and GATT treaties killed the printed circuit industry so I shut it down about ten years ago. Now I work from my home shop with a much smaller system using brush plating, several small tanks, and the evaporator. All of this is home made from PVC plastic and some stainless. My evaporator is a 40 gallon stainless tank with a 6 kW electric heater. It's totally enclosed and uses a venturi blower so the blower blades never get contaminated with fumes. The rotating metal disks in the tanks are powered by a small gear motor and turn very slowly. Their function is to bring waste water into the air flow through the tank. This evaporator tanks is nothing more than a glorified humidifier.

A couple of times a year I'll let the tank boil down to a sludge and scrape it into a bucket. The most I've ever collected was about four gallons in a year. When they have the local waste collection day I take it there and they gladly accept it. When I had the plant running I sold all concentrated waste to a chemical company that refined it for use in treating lumber. They were glad to buy it since the copper content was very high. Since I sold it I had no liability and we never once landfilled any sludge.

As to cyanide, Evan pretty much laid out the details. It's not dangerous to do if you're careful. I used gold plating solutions from Engelhard that were cyanide based. The main thing was to never get it on you or near any acids. The salesman said cyanide gas smells like roasting almonds and if we ever smelled that to get outside quickly. One of my plating guy's asked if we should take the time to drag out anyone near death or dead and he said "hell no, they're on their own!" That put the fear into all of us and we never had a problem. That salesman told me later it wasn't that big of a deal but he was just making it clear as to the potential danger. So just be careful, wear gloves and safety glasses and cyanide based solutions won't be a problem.