- Email: [email protected]
Heard on the hotline
Join us a http://www.finishing.com/l.etters
F
or the last few months we’ve been featuring anodizing, patinization, home plating, school plating-just about everything but industrial plating. So this month we’ll try to put most of the focus back onto industrial plating problems. NONCYANIDE
CADMIUM
Is there a noncyanide cadmium plating bath that will meet the requirements of Mil Standard QQ-P-416’? Scott Clements clementsjBala.usmc.mil I hope not. I am helping to install more cyanide cadmium capacity in New Jersey as we speak, but I will keep an ear tuned to this letter. Tom Pullizzi Team*Faraday [email protected] Back around Rev F of QQ -P-416, brightener was banned because it contributed to hydrogen embrittlement. This rev ignored the fact that there was another military specification for low hydrogen embrittlement. Brightener is a necessary part of the package for acid cadmium to work. Delete the brightener and you eliminate acid cadmium as a possible substitnte for cyanide cadmium. 1 have used one process with quite good luck and have E-mailed the supplier’s name. The company that acquired the process quit making it due to reduced demand and high cost of manufacture. Another one uses pyridine and thus stinks like dead fish. There are generic recipes for fluoborate cadmium and one that I tried worked but, again, required a brightener or it was a very ugly finish. James Watts James Watts Inc. [email protected] BRIGHT
AClD CbPPER
BRIGHTENER
PROBLEM
We once had a three-part brightener; we now have a single-part brightener. I don’t think I have the same control. Does anyone have suggestions as to what is the best? Mick Long Auscraft Medals [email protected] The question is whether you know how much of each component to add, not whether you have more components. 56
0 Copyright
Elsevier
If you are going by the appearance of parts or by a simple Hull cell test the single “premixed” brightener is better. If you have analytical instruments like CVS or HPLC that can distinguish between the effects of different components then the multiadditive system is better. Control is based on analysis. Bill Vins [email protected] With acid copper plating processes it really depends on the system you are using. The older dye-based systems used a single additive and were very successful for many years and were very easy to run. The newer systems with multiple additives give a much wider operating range and can be controlled with a Hull cefl once you understand the interaction of the components and the function of each of the components. Although a machine like a HPLC would be of much use in controlling an acid copper solution, at the substantial cost involved in its purchase I doubt that you could mount a case for the purchase to your boss. If you need any help E-mail me personally with your phone number and we can talk about your problems. John Tenison-Woods Peninsula Metal Finishing Cons P/L [email protected]
TIN-NICKEL
CO-DEPOSIT
We are a small job shop and are interested in possible plating of tin-nickel codeposit. We know little of this alloy. What are the good points, the pitfalls, and the stability and repeatability of the process? Where can the baths be purchased and any other technical information obtained? Tom McLaughlin Accutek Inc. [email protected] Tin-nickel plating has been around for a long time and is used in some instances as a protective coat where chromium is unacceptable. It has several problems associated with its use: the solution and its fumes are extremely corrosive to both the environment and to people; the solution is tluoridecontaining (added as ammonium bifluoride), and the fumes are fairly toxic. The finish itself needs to be applied at greater than 20 microns thick to be of any real use. John Tenison-Woods Peninsula Metal Finishing Cons P/L [email protected] Science
Inc.
METAL
FINISWING
.
AUGUST
1998
PLATING
PLASTIC
I am trying to find a company that can plate a plastic part fabricated using stereolithography. The part is a lattice structure 6 in. X 6 in. X 2 in., with each row of the lattice being approximately 0.020 in. thick. We want to plate the part to make the part conductive and also structurally rigid. Any feedback is much appreciated. Direct E-mail welcome. Matt Gordon [email protected] I have E-mailed you the names of a prototype shop and a production shop. Typically, plated coatings are stressed and are not designed to impart structural rigidity; however, it is possible to deposit thick unstressed metal, typically nickel from a sulfamate plating solution. The term “electroforming” is used to describe actually building a part from an electrodeposited coating, and that seems to be pretty much what you are describing here. Ted Mooney Finishing Technolagy [email protected]
ANODIZING
BRASS AIR PtSTOL
PARTS
I have an old air pistol that I’d like to restore, but before I do that I’d like to have it anodized because the original brass finish is badly worn. None of the gunsmiths or repair shops in my area can do anodizing nor know anyone who can. I live in the Texas Panhandle and would like to find someone as close as possible. Can you help me? Terry Pevehouse [email protected] I think there is a bit of confusion here. To my knowledge brass is not anodized. Anodizing is an accelerated oxidation process that is used on substrates like aluminum, titanium, and magnesium-not brass. If the air pistol is aluminum with a brasslike color, yes, you could have it reanodized and dyed again. If it is solid brass you would just have it cleaned and relacquered. If it is brass-plated steel you could have it replated. Ted Mooney Finishing Technology [email protected]
SULFATE
MYSTERY
We have started a new nickel/chrome facility. To start with 1 added sulfuric acid to make the required ratio of 2OO:I but I found in the lab that it is nearly 34O:l and showing just half the sulfate addition. I could not understand where 1 am losing my sulfate. My supplier has given the explanation that I have lost it as lead sulfate at the lead anodes (they are not new) and some of the sulfate has settled down on the walls of the tank,.which is a brand new PVC lining. I don’t agree with this explanation as I have started several new chrome baths in hard chrome with new linings, etc., but never observed such amazing results. One more thing; initially 1 started with gradual addition of sulfate and the results were matching with theoretical values but after 2 to 3 days of trials the sulfate reduced drastically but the
Pound-for-pound, TMax~ mayLc the world’smostefficimt heatexchrger. Proof that good things do indeed come in small packages, the TherMax* heat exchanger from Process Technology has capabilities that far outweigh its unassuming size. Enhanced turbulence created by a unique spiral plate design helps make TherMax* extremely efficient. These compact cylinders are available in exchange area capacities ranging from 1.1 to 15 square feet. Call us today to get all the details on how this mighty mite can make a big difference in your specific process.
800-621-1998 (OH) l 800-621-1999 (CA) FAX: 440-974-9561 (OH) l 714-935-0598 (CA)
www.process-tec:hnology.com Circfe 067 on reader
METAL FINISHING . AUGUST 1998
information
cad
57
The National Association of Metal Finishers is p/eased to announce a unique setting for it’s 1999 Annual Convention 81 Management Seminars! Join fellow industry representatives for an unforgettable, luxurious 7-day cruise out of San Juan, Puerto Rico deep into the Caribbean on Celebrity Cruise Lines’ “Gafaxy” and visit such exotic ports of call as St. Lucia, Barbados, Martinique, Antigua and St. Thomas. Ensure the best available accommodations for this exciting convention cruise experience by reserving your cabin today! Call the Association ‘s official 1999 Convention Cruise travel agent, Sundial Travel, at (800) 287-64 1 1, or visit the NAM F’s website at www.namforg. Full convention program information and registration materials wilt be available soon.
February
27
Circk 58
- March
092 on reader
hfommtbn
6,1999
card
parts are still coming out fine, maybe because of the 65 ppm chloride content in my chrome bath. I would like to point out that this particular bath had 200 ppm of chloride in the beginning, which I removed by high current density purification at the anode and a subsequent addition of 5 lb of silver oxide. Please suggest where I lost my sulfate and for how long this trend will be continued. Hemant Bansal Olympic Coater Inc. [email protected] Interesting problem! It sounds like your chromium solution may not have been a brand new make up. This supposition is based on the fact that you had high chloride contamination. If your solution came from another plating facility, knowing its history would be very helpful. For example if it had been a self-regulating, high-speed (SRHS) chromium, the solution could be over suppressed. SRHS chromium solutions contained ingredients that helped control the sulfate and secondary catalyst if they started to get too high. These special ingredients would actually cause the sulfate to precipitate if it got out of range. If the sulfate got too low, it would allow the sulfate to come back into solution-thus the “SR” part of the name. if, however, excessive amounts of these special ingredients got into the solution, the sulfate content of the solution would be suppressed to a level below where acceptable work could be plated. I’?) correct the condition we would have to keep adding sulfate until we had consumed the excess special goodie. This is one of a few scenarios that could be causing your problem. The important point is that if your solution came from another shop you should investigate its history, as it may point to the answer. If it’s a new make up, that presents a more interesting problem. Ken Lemke Canadian Finishing Systems Ltd. [email protected]
COPPER/NICKEL BARREL ON DIE CAST ZINC
PLATING
I have a problem barrel plating small, die cast zinc details. It seems that heavy loads in the barrel (approximately 15-20 kg or 38-40 lbs) “grinds” off the copper layer at sharp comers and edges. The rotation speed of the barrel is approximately 9 t-pm, time in the copper bath 40 min, with full rotation all the time. This results in etching of the base metal in the following process, black “pores” on the finished detail and contamination of the nickel bath. Has anyone had this problem, and if so, how did you solve it? (Not reducing the load of the barrel.) This problem can also be seen as black dots, growing in size over time, if the die cast detail is immersed in dilute hydrochloric acid at the laboratory directly after the copper strike. Jesper Km&son Markaryds Y&handling AB [email protected] You have described the problem fairly clearly, but I can’t think of any resolution that does not involve plating the copper faster so that it buiIds up faster than it is worn down. METAL FINISHING
l
AUGUST 1998
In turn I don’t know how you would do this unless you either reduce the load or increase the amperage (assuming you can do so without burning), or use two copper steps (a short strike in a cyanide or proprietary pyrophosphate, followed by plating in a high-build acid copper bath). Ted Mooney Finishing Technology [email protected] The barrel rotation speed seems high. Try reducing the speed to 4 to 6 rpm. Richard Painter Pavco wamba813Gaol.com Your barrel speed is quite high, abnormally so even. 1 agree with Mr. Painter that you should slow it down, 4 to 6 rpm if not slower, down to 2 to 3 ‘pm. Since you’re having problems also try some media; copper plated balls can do wonders for helping parts not beat each other up. Ron Landrette B&P Plating Supply [email protected] Thank you for the tips, I’11 surely consider them carefully, and we’re about to adjust the barrel rotation speed. I’11 report the result. Jesper Knutsson Markaryds Ytbebandling AB jesper.knutsson@%arkaryd.mail.telia.com
FASTER
NICKEL
this higher pH. You will uselessbrightener and will need to reducethe feed rate. Tom PulIizzi Team*Faraday [email protected] Tom is right. If nothing was wrong with your measurement or calculation in the surfaceareaof parts in your barrel the power you usedwas far beyond the range specified. The major portion of electricity was consumed in hydrogen evolution in your case. This is why the coating thickness was much lower than you expected. The low pH also acceleratedhydrogen evolution. Significant hydrogen evolution would deteriorate the nickel deposit and cause bydrogen embrittlement. L. Hao [email protected] Ted Mooney is an independentconsultingengineerbasedin YF Kinnelon,N.J. WMTOWRITEFORMElXLHNTSHlNGl Call or write to requesta copy of our guidelinesfor authors,or simply contact the editor at MFcALpINEsm 66OWhite Plains Rd., Tarrytown,NY 10591 Phone 914-333-2571 l Fax 914-333-2570
DEPOSIT
Our nickel bath is: nickel sulfate, 35 oz/gal; nickel cbloride, 13 ox/gal; boric acid, 7 ox/gal; pH is 3.5 to 4.2; metal by analysis is 11 to I2 ox/gal. With 22 f? of surface in the barrel at 500 A for 30 min, the metal deposit was O.OOQO3 in.; also with 55 min in the bath the deposit was 0.00009 in. Our client is asking for 0.0002 to 0.00025 in. Is there anything we can and should do to achieve this deposit in less time than what it is taking right now? Wilbert E. Me&ma Antilles Electroplating Inc. [email protected] I did no calculations for your problem but something is very wrong. Barrel plating of bright or Watts nickel should occur at around 1 to 4 A/f? (average) of surface area. At 1 A/# you would need 3.8 A-hr to deposit O.OOtXl2in. of nickel on an area of I ft? (at 100% efficiency, not a bad estimate for nickel plating, it is actually a little less efficient); 3.8 A-hr X 22 ft? = 83.6 A-hr. If the setting on your rectifier’s ampere meter is 22 A, then it would take about 4 hours to plate the minimum amount of O.ooO2 in. of nickel. So at 4 A/I? it should take about 1 hour to deposit the same amount. People do plate at 1 A/f?, average, when they want the best throwing power of the bath and best ductility of deposit. For commercial plating of bright hardware you will probably opt for speed(lower cost) over achieving the finest me&an&I propertiesof the deposit. Unlessyou have specialductility problemsallow the pH to rise to 4.2 to 4.4. The brightenerand the pH buffer work better at Circle 080
METAL
FINISHING
l
AUGUST
1998
on maderinformatii
card 59
F
or the last few months we’ve been featuring anodizing, patinization, home plating, school plating-just about everything but industrial plating. So this month we’ll try to put most of the focus back onto industrial plating problems. NONCYANIDE
CADMIUM
Is there a noncyanide cadmium plating bath that will meet the requirements of Mil Standard QQ-P-416’? Scott Clements clementsjBala.usmc.mil I hope not. I am helping to install more cyanide cadmium capacity in New Jersey as we speak, but I will keep an ear tuned to this letter. Tom Pullizzi Team*Faraday [email protected] Back around Rev F of QQ -P-416, brightener was banned because it contributed to hydrogen embrittlement. This rev ignored the fact that there was another military specification for low hydrogen embrittlement. Brightener is a necessary part of the package for acid cadmium to work. Delete the brightener and you eliminate acid cadmium as a possible substitnte for cyanide cadmium. 1 have used one process with quite good luck and have E-mailed the supplier’s name. The company that acquired the process quit making it due to reduced demand and high cost of manufacture. Another one uses pyridine and thus stinks like dead fish. There are generic recipes for fluoborate cadmium and one that I tried worked but, again, required a brightener or it was a very ugly finish. James Watts James Watts Inc. [email protected] BRIGHT
AClD CbPPER
BRIGHTENER
PROBLEM
We once had a three-part brightener; we now have a single-part brightener. I don’t think I have the same control. Does anyone have suggestions as to what is the best? Mick Long Auscraft Medals [email protected] The question is whether you know how much of each component to add, not whether you have more components. 56
0 Copyright
Elsevier
If you are going by the appearance of parts or by a simple Hull cell test the single “premixed” brightener is better. If you have analytical instruments like CVS or HPLC that can distinguish between the effects of different components then the multiadditive system is better. Control is based on analysis. Bill Vins [email protected] With acid copper plating processes it really depends on the system you are using. The older dye-based systems used a single additive and were very successful for many years and were very easy to run. The newer systems with multiple additives give a much wider operating range and can be controlled with a Hull cefl once you understand the interaction of the components and the function of each of the components. Although a machine like a HPLC would be of much use in controlling an acid copper solution, at the substantial cost involved in its purchase I doubt that you could mount a case for the purchase to your boss. If you need any help E-mail me personally with your phone number and we can talk about your problems. John Tenison-Woods Peninsula Metal Finishing Cons P/L [email protected]
TIN-NICKEL
CO-DEPOSIT
We are a small job shop and are interested in possible plating of tin-nickel codeposit. We know little of this alloy. What are the good points, the pitfalls, and the stability and repeatability of the process? Where can the baths be purchased and any other technical information obtained? Tom McLaughlin Accutek Inc. [email protected] Tin-nickel plating has been around for a long time and is used in some instances as a protective coat where chromium is unacceptable. It has several problems associated with its use: the solution and its fumes are extremely corrosive to both the environment and to people; the solution is tluoridecontaining (added as ammonium bifluoride), and the fumes are fairly toxic. The finish itself needs to be applied at greater than 20 microns thick to be of any real use. John Tenison-Woods Peninsula Metal Finishing Cons P/L [email protected] Science
Inc.
METAL
FINISWING
.
AUGUST
1998
PLATING
PLASTIC
I am trying to find a company that can plate a plastic part fabricated using stereolithography. The part is a lattice structure 6 in. X 6 in. X 2 in., with each row of the lattice being approximately 0.020 in. thick. We want to plate the part to make the part conductive and also structurally rigid. Any feedback is much appreciated. Direct E-mail welcome. Matt Gordon [email protected] I have E-mailed you the names of a prototype shop and a production shop. Typically, plated coatings are stressed and are not designed to impart structural rigidity; however, it is possible to deposit thick unstressed metal, typically nickel from a sulfamate plating solution. The term “electroforming” is used to describe actually building a part from an electrodeposited coating, and that seems to be pretty much what you are describing here. Ted Mooney Finishing Technolagy [email protected]
ANODIZING
BRASS AIR PtSTOL
PARTS
I have an old air pistol that I’d like to restore, but before I do that I’d like to have it anodized because the original brass finish is badly worn. None of the gunsmiths or repair shops in my area can do anodizing nor know anyone who can. I live in the Texas Panhandle and would like to find someone as close as possible. Can you help me? Terry Pevehouse [email protected] I think there is a bit of confusion here. To my knowledge brass is not anodized. Anodizing is an accelerated oxidation process that is used on substrates like aluminum, titanium, and magnesium-not brass. If the air pistol is aluminum with a brasslike color, yes, you could have it reanodized and dyed again. If it is solid brass you would just have it cleaned and relacquered. If it is brass-plated steel you could have it replated. Ted Mooney Finishing Technology [email protected]
SULFATE
MYSTERY
We have started a new nickel/chrome facility. To start with 1 added sulfuric acid to make the required ratio of 2OO:I but I found in the lab that it is nearly 34O:l and showing just half the sulfate addition. I could not understand where 1 am losing my sulfate. My supplier has given the explanation that I have lost it as lead sulfate at the lead anodes (they are not new) and some of the sulfate has settled down on the walls of the tank,.which is a brand new PVC lining. I don’t agree with this explanation as I have started several new chrome baths in hard chrome with new linings, etc., but never observed such amazing results. One more thing; initially 1 started with gradual addition of sulfate and the results were matching with theoretical values but after 2 to 3 days of trials the sulfate reduced drastically but the
Pound-for-pound, TMax~ mayLc the world’smostefficimt heatexchrger. Proof that good things do indeed come in small packages, the TherMax* heat exchanger from Process Technology has capabilities that far outweigh its unassuming size. Enhanced turbulence created by a unique spiral plate design helps make TherMax* extremely efficient. These compact cylinders are available in exchange area capacities ranging from 1.1 to 15 square feet. Call us today to get all the details on how this mighty mite can make a big difference in your specific process.
800-621-1998 (OH) l 800-621-1999 (CA) FAX: 440-974-9561 (OH) l 714-935-0598 (CA)
www.process-tec:hnology.com Circfe 067 on reader
METAL FINISHING . AUGUST 1998
information
cad
57
The National Association of Metal Finishers is p/eased to announce a unique setting for it’s 1999 Annual Convention 81 Management Seminars! Join fellow industry representatives for an unforgettable, luxurious 7-day cruise out of San Juan, Puerto Rico deep into the Caribbean on Celebrity Cruise Lines’ “Gafaxy” and visit such exotic ports of call as St. Lucia, Barbados, Martinique, Antigua and St. Thomas. Ensure the best available accommodations for this exciting convention cruise experience by reserving your cabin today! Call the Association ‘s official 1999 Convention Cruise travel agent, Sundial Travel, at (800) 287-64 1 1, or visit the NAM F’s website at www.namforg. Full convention program information and registration materials wilt be available soon.
February
27
Circk 58
- March
092 on reader
hfommtbn
6,1999
card
parts are still coming out fine, maybe because of the 65 ppm chloride content in my chrome bath. I would like to point out that this particular bath had 200 ppm of chloride in the beginning, which I removed by high current density purification at the anode and a subsequent addition of 5 lb of silver oxide. Please suggest where I lost my sulfate and for how long this trend will be continued. Hemant Bansal Olympic Coater Inc. [email protected] Interesting problem! It sounds like your chromium solution may not have been a brand new make up. This supposition is based on the fact that you had high chloride contamination. If your solution came from another plating facility, knowing its history would be very helpful. For example if it had been a self-regulating, high-speed (SRHS) chromium, the solution could be over suppressed. SRHS chromium solutions contained ingredients that helped control the sulfate and secondary catalyst if they started to get too high. These special ingredients would actually cause the sulfate to precipitate if it got out of range. If the sulfate got too low, it would allow the sulfate to come back into solution-thus the “SR” part of the name. if, however, excessive amounts of these special ingredients got into the solution, the sulfate content of the solution would be suppressed to a level below where acceptable work could be plated. I’?) correct the condition we would have to keep adding sulfate until we had consumed the excess special goodie. This is one of a few scenarios that could be causing your problem. The important point is that if your solution came from another shop you should investigate its history, as it may point to the answer. If it’s a new make up, that presents a more interesting problem. Ken Lemke Canadian Finishing Systems Ltd. [email protected]
COPPER/NICKEL BARREL ON DIE CAST ZINC
PLATING
I have a problem barrel plating small, die cast zinc details. It seems that heavy loads in the barrel (approximately 15-20 kg or 38-40 lbs) “grinds” off the copper layer at sharp comers and edges. The rotation speed of the barrel is approximately 9 t-pm, time in the copper bath 40 min, with full rotation all the time. This results in etching of the base metal in the following process, black “pores” on the finished detail and contamination of the nickel bath. Has anyone had this problem, and if so, how did you solve it? (Not reducing the load of the barrel.) This problem can also be seen as black dots, growing in size over time, if the die cast detail is immersed in dilute hydrochloric acid at the laboratory directly after the copper strike. Jesper Km&son Markaryds Y&handling AB [email protected] You have described the problem fairly clearly, but I can’t think of any resolution that does not involve plating the copper faster so that it buiIds up faster than it is worn down. METAL FINISHING
l
AUGUST 1998
In turn I don’t know how you would do this unless you either reduce the load or increase the amperage (assuming you can do so without burning), or use two copper steps (a short strike in a cyanide or proprietary pyrophosphate, followed by plating in a high-build acid copper bath). Ted Mooney Finishing Technology [email protected] The barrel rotation speed seems high. Try reducing the speed to 4 to 6 rpm. Richard Painter Pavco wamba813Gaol.com Your barrel speed is quite high, abnormally so even. 1 agree with Mr. Painter that you should slow it down, 4 to 6 rpm if not slower, down to 2 to 3 ‘pm. Since you’re having problems also try some media; copper plated balls can do wonders for helping parts not beat each other up. Ron Landrette B&P Plating Supply [email protected] Thank you for the tips, I’11 surely consider them carefully, and we’re about to adjust the barrel rotation speed. I’11 report the result. Jesper Knutsson Markaryds Ytbebandling AB jesper.knutsson@%arkaryd.mail.telia.com
FASTER
NICKEL
this higher pH. You will uselessbrightener and will need to reducethe feed rate. Tom PulIizzi Team*Faraday [email protected] Tom is right. If nothing was wrong with your measurement or calculation in the surfaceareaof parts in your barrel the power you usedwas far beyond the range specified. The major portion of electricity was consumed in hydrogen evolution in your case. This is why the coating thickness was much lower than you expected. The low pH also acceleratedhydrogen evolution. Significant hydrogen evolution would deteriorate the nickel deposit and cause bydrogen embrittlement. L. Hao [email protected] Ted Mooney is an independentconsultingengineerbasedin YF Kinnelon,N.J. WMTOWRITEFORMElXLHNTSHlNGl Call or write to requesta copy of our guidelinesfor authors,or simply contact the editor at MFcALpINEsm 66OWhite Plains Rd., Tarrytown,NY 10591 Phone 914-333-2571 l Fax 914-333-2570
DEPOSIT
Our nickel bath is: nickel sulfate, 35 oz/gal; nickel cbloride, 13 ox/gal; boric acid, 7 ox/gal; pH is 3.5 to 4.2; metal by analysis is 11 to I2 ox/gal. With 22 f? of surface in the barrel at 500 A for 30 min, the metal deposit was O.OOQO3 in.; also with 55 min in the bath the deposit was 0.00009 in. Our client is asking for 0.0002 to 0.00025 in. Is there anything we can and should do to achieve this deposit in less time than what it is taking right now? Wilbert E. Me&ma Antilles Electroplating Inc. [email protected] I did no calculations for your problem but something is very wrong. Barrel plating of bright or Watts nickel should occur at around 1 to 4 A/f? (average) of surface area. At 1 A/# you would need 3.8 A-hr to deposit O.OOtXl2in. of nickel on an area of I ft? (at 100% efficiency, not a bad estimate for nickel plating, it is actually a little less efficient); 3.8 A-hr X 22 ft? = 83.6 A-hr. If the setting on your rectifier’s ampere meter is 22 A, then it would take about 4 hours to plate the minimum amount of O.ooO2 in. of nickel. So at 4 A/I? it should take about 1 hour to deposit the same amount. People do plate at 1 A/f?, average, when they want the best throwing power of the bath and best ductility of deposit. For commercial plating of bright hardware you will probably opt for speed(lower cost) over achieving the finest me&an&I propertiesof the deposit. Unlessyou have specialductility problemsallow the pH to rise to 4.2 to 4.4. The brightenerand the pH buffer work better at Circle 080
METAL
FINISHING
l
AUGUST
1998
on maderinformatii
card 59