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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Chrome Plating question
Most of our plating is O D on large rings ... but recently a job was set up
for I D. The O D rings are about 20" and we have 12 anodes in the tank. Plating is done at 1900 amps The I D rings are the same size but we only use one 3" anode in the center of the rings The supervisor claims they did this job before and never had a problem getting 1900 amps but the most I can get is 1100 amps at 20 volts max for rectifier I believe it's my lack of surface area but he says " We never had a problem before " I checked the unit with an OD dummy load and have no problem getting 3000 amps so I know the units capable of supplying the current Tom |
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Check to ensure that connections are tight and clean. A few
thousanths of a ohm of resistance in a connection or bussbar would cost you several volts at the current levels you're working with. I'll say up front that I have zero experience with chrome plating, but I see a big difference between 12 anodes and one anode. More anode area will present less resistance (and heating) in the tank. Scaling things to my experience at the 1-amp level with nickel, copper and zinc, I'm quite sure that an .003" dia anode would not work well. I'd bet you're right that you need a lot more anode surface area than a 3" dia anode of given length provides. On Wed, 01 Dec 2004 04:33:20 GMT, "invntrr" wrote: Most of our plating is O D on large rings ... but recently a job was set up for I D. The O D rings are about 20" and we have 12 anodes in the tank. Plating is done at 1900 amps The I D rings are the same size but we only use one 3" anode in the center of the rings The supervisor claims they did this job before and never had a problem getting 1900 amps but the most I can get is 1100 amps at 20 volts max for rectifier I believe it's my lack of surface area but he says " We never had a problem before " I checked the unit with an OD dummy load and have no problem getting 3000 amps so I know the units capable of supplying the current Tom |
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On Wed, 01 Dec 2004 04:33:20 GMT, "invntrr"
wrote: Most of our plating is O D on large rings ... but recently a job was set up for I D. The O D rings are about 20" and we have 12 anodes in the tank. Plating is done at 1900 amps The I D rings are the same size but we only use one 3" anode in the center of the rings The supervisor claims they did this job before and never had a problem getting 1900 amps but the most I can get is 1100 amps at 20 volts max for rectifier I believe it's my lack of surface area but he says " We never had a problem before " I checked the unit with an OD dummy load and have no problem getting 3000 amps so I know the units capable of supplying the current Tom Sounds like thats all the surface area of the anode can handle. But then I dont know dick about plating. Gunner "I mean, when's the last time you heard of a college where the Young Republicans staged a "Sit In" to close down the Humanities building? On the flip side, how many sit in's were staged to close the ROTC building back in the '60's? Liberals stage protests, do civil disobedience, etc. Conservatives talk politely and try to work out a solution to problems through discourse until they believe that talking won't work... they they go home and open the gun cabinets. Pray things never get to the point where the conservatives decide that "civil disobedience" is the next step, because that's a very short route to "voting from the rooftops" Jeffrey Swartz, Misc.Survivalism |
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"Don Foreman" wrote in message ... Check to ensure that connections are tight and clean. A few thousanths of a ohm of resistance in a connection or bussbar would cost you several volts at the current levels you're working with. I have 18.5 volts between the anode and ring ... a 1.5 volt drop from source at 1100 amps that is about what I would expect. We use 4.0"x0.5" bus I'll say up front that I have zero experience with chrome plating, but I see a big difference between 12 anodes and one anode. More anode area will present less resistance (and heating) in the tank. Ya ... I agree Scaling things to my experience at the 1-amp level with nickel, copper and zinc, I'm quite sure that an .003" dia anode would not work well. I'd bet you're right that you need a lot more anode surface area than a 3" dia anode of given length provides. It's a 3.0" anode It's another alien abduction story ... the supervisor really believes he did the job this way but something had to have changed. Ohm's Law has yet to be broken . Tom On Wed, 01 Dec 2004 04:33:20 GMT, "invntrr" wrote: Most of our plating is O D on large rings ... but recently a job was set up for I D. The O D rings are about 20" and we have 12 anodes in the tank. Plating is done at 1900 amps The I D rings are the same size but we only use one 3" anode in the center of the rings The supervisor claims they did this job before and never had a problem getting 1900 amps but the most I can get is 1100 amps at 20 volts max for rectifier I believe it's my lack of surface area but he says " We never had a problem before " I checked the unit with an OD dummy load and have no problem getting 3000 amps so I know the units capable of supplying the current Tom |
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"invntrr" wrote in message news:kQbrd.2815$M57.1849@trnddc01... Most of our plating is O D on large rings ... but recently a job was set up for I D. The O D rings are about 20" and we have 12 anodes in the tank. Plating is done at 1900 amps The I D rings are the same size but we only use one 3" anode in the center of the rings The supervisor claims they did this job before and never had a problem getting 1900 amps but the most I can get is 1100 amps at 20 volts max for rectifier I believe it's my lack of surface area but he says " We never had a problem before " I checked the unit with an OD dummy load and have no problem getting 3000 amps so I know the units capable of supplying the current Tom My platers handbook says the current density range for hard chrome is 288-432 ASF @ 6-12 Volts and 130 degrees F. Plating at the higher voltage might be causing so much gassing at the anode, your not able to pass the current required. Ed Angell |
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Remember that there is a current range needed for best plating per square
inch of plating areal. If you are plating less area then you don't need as much current. You also need to have the necessary area of electrodes in the bath to get that current in addition. -- Why isn't there an Ozone Hole at the NORTH Pole? |
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Thanks guy .... We have done chrome plating for over 50 years with probably
3 to 4 million units shipped. The problem I'm having has everything to do with total area ... however , this old timer is telling me this particular job was done before with no problems ... I say bull**** !... something has changed since the last time they did it. I have 18.5 VDC at the work and can only draw 1100 amps. It's a straight DC calculation using Ohms Law ... always has been and always will be. My surface area is too small to draw the proper current ...but I can't get that through the guys head "Bob May" wrote in message ... Remember that there is a current range needed for best plating per square inch of plating areal. If you are plating less area then you don't need as much current. You also need to have the necessary area of electrodes in the bath to get that current in addition. -- Why isn't there an Ozone Hole at the NORTH Pole? |
#8
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Try a hollow anode of the same size...
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Ed - What's the title of your platers handbook? I've been looking for one
and would like to hear any opinions. Hul Ed Angell wrote: : My platers handbook says the current density range for hard chrome is : 288-432 ASF @ 6-12 Volts and 130 degrees F. Plating at the higher voltage : might be causing so much gassing at the anode, your not able to pass the : current required. : : Ed Angell : : -- - for email, put the word "keep" in subject line - |
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Hul, I tried to send this to you direct and it got rejected. The handbook
is a 1960 edition of the Los Angeles chapter "Platers Handbook" sponsored by the American Electroplaters Society. It's pretty basic and not a bad piece of information. Ed Angell "Hul Tytus" wrote in message ... Ed - What's the title of your platers handbook? I've been looking for one and would like to hear any opinions. Hul Ed Angell wrote: : My platers handbook says the current density range for hard chrome is : 288-432 ASF @ 6-12 Volts and 130 degrees F. Plating at the higher voltage : might be causing so much gassing at the anode, your not able to pass the : current required. : : Ed Angell : : -- - for email, put the word "keep" in subject line - |
#11
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Ed, thanks for the info.
Sorry about the rejection - the mail reader is a new one. Ed Angell wrote: : Hul, I tried to send this to you direct and it got rejected. The handbook : is a 1960 edition of the Los Angeles chapter "Platers Handbook" sponsored by : the American Electroplaters Society. It's pretty basic and not a bad piece : of information. : : Ed Angell : |
#12
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On Wed, 01 Dec 2004 21:06:36 GMT, "invntrr"
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email Thanks guy .... We have done chrome plating for over 50 years with probably 3 to 4 million units shipped. Which he did not know, and you asked for help. Bit sarky! |
#13
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"Old Nick" wrote in message ... On Wed, 01 Dec 2004 21:06:36 GMT, "invntrr" vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email Thanks guy .... We have done chrome plating for over 50 years with probably 3 to 4 million units shipped. Which he did not know, and you asked for help. Bit sarky! I'm just a lowly tech and know little about plating ... when I say " WE " I mean the company . The supervisor is giving me a lot of crap on an I D job and based on my calculations using Ohms Law he will never get 2000 amps ... something must have changed since the last time they did the job 2-3 years ago Specific Gravity of bath... surface area ... something but I can't figure it out , that's why I asked for advice. I can get 3000+ amps on an O D job so the rectifier is working good. Tom |
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