- Email: [email protected]
Heard on the hotline
Heard on the Hotline by Ted Mooney, P.E.
Contact us at http://www.finishing.com/letters
A
s you can see, we now include the E-mail addresses of the participants in the Hotline discussions so that readers can respond immediately and directly to any of the inquiries here; I would appreciate if you would copy [email protected] on any such direct responses. If you’re not using E-mail yet, do yourself the favor of looking into it today. Once you’ve used it, you’ll never go back to time-consuming letters and faxes except when you absolutely must; E-mail is not only faster, easier, less intrusive, and much less expensive, but, with a properly set-up E-mail account, you’ll automatically have a smooth efficient filing system that lets you easily find and review any letter you have ever sent or received. We’ve mentioned several times in recent months that Internet usage is growing explosively. One piece of fallout, though, is that traffic on dial-up BBS’s is drying up to the extent that they no longer have critical mass. Consequently, at about the time you read this, we will be pulling the plug on the BBS; so we ask you to use Internet access exclusively. The World Wide Web address of the Hotline is http://www.finishing.com/letters.
SUBSTITUTES
FOR MEK
Can anyone identify/reference products and companies that can substitute for methyl ethyl ketone (MEK)? The application is our paint booth clean-up. We need to clean the pipes, equipment, and other items and would like to eliminate the use of MEK. Dave Reim, Tech Resources Inc., 75430.53 [email protected] I don’t do industrial painting for a living but have had experience through the years analyzing paints, as well as trying to strip them. There are a number of ways to remove paint, depending upon what the paint is and what the paint is on. Start with contacting the paint supplier and asking for answers. Some of the nonflammable solvents that would work the best are either restricted (l,l, 1-trichloroethane) or carcinogenic (trichloroethylene, methylene chloride). Others are flammable (acetone), flammable and carcinogenic (toluene), or flammable and otherwise toxic (butyl cellosolve). There are the caustic-type strippers based upon sodium hydroxide that don’t dissolve but actually chemically destroy the paint (saponification). You can bum off the paint in a furnace, or use a molten salt bath to do the same thing. Finally, you can blast off the paint using walnut shells or other media in a “sandblaster.” No matter what route you follow, you end up with a potentially hazardous waste. Be METAL FINISHING
??
JULY 1996
0 Copyright
sure to check with your local regulatory agencies before trying to get rid of the final cleanup byproducts. Bill Vins, [email protected] For further options for stripping, case on page 23.
see the Product Show-
FILTER PRESS FOR WASTEWATER
TREATMENT
We have started running a filter press on our pH adjusted wastewater, containing mostly nickel. At pH about 10.5 to 11 .O, we form a decent amount of precipitate, which sort of goes through the filter-press cloth instead of staying on it. Is there a particular cloth weight/density, or whatever measure is commonly applied here, that works well on hydroxides, or would it be advisable to use a filter aid, flocculent, or some other technique to prevent the breakthrough? Berl Stein, b.stein3Qgenie.geis.com I think you need to generate a larger particle size. The filter press cloth is probably quite coarse and most unflocculated metal hydroxides are pretty fine. You should be able to see the floes form as the flocculating agent mixes in. Just don’t overdose, as it will turn the sludge into a slimy mess. Almost any industrial chemical supplier can provide the flocculating agent, probably an anionic agent will work best. Do a jar test first (waste sample in beaker, very small amount of agent added per manufacturer’s dosing rates, mix, and voila-flocculated sludge). Jar tests are good for evaluating different types/manufacturers. You may even get enough in the samples to do the whole job! Bill Vins, [email protected] With regard to the nickel hydroxide precipitate, I would definitely use a filter aid, such as diatomaceous earth, to precoat the cloth. This should prevent leak-through of the precipitate. Rocky C. Costello, PE, [email protected] I’ve used filter presses without filter aid in batch treatment of cleaner dumps, acid dips, and chromates many times and found that the suspended solids slipping through the press were always lower than the suspended solids coming out of the clarifier-such that it didn’t make sense to steer the effluent back through the clarifier and “ruin it.” But in treating a dilute stream, the coarse-woven polypropylene cloth is apparently insufficient. I’ve seen, but haven’t used, a molded membrane-type filter cloth that is very
Elsevier Science Inc.
smooth and shiny on one side, with a heavy flocked finish on the other side; it may be Tyvek. The strange thing is that the vendor didn’t seem to know quite what it is, or even whether the shiny side or flocked side is intended to face out as the filtering surface. If anybody has used such a product, or knows knowledgeable sources for it, I’d like to hear from them. Ted Mooney, Finishing Technology, N.J., [email protected] BATCH TREATMENT
OF CHROMIC
ACID WASTE
I was recently involved in the treatment of a batch of chromium. I work in the waste treatment department of a shop that does electroless plating on plastics. We had some chromic acid, which we use to “rough up” the parts that are plated with copper and nickel. We put about 500 gal or so of this chromic acid in our 3,000-gal batch tank. We had around 47,000 ppm chromium in this batch. We ended up having to treat this batch with about 2,500 lb of sodium metabisulfite. We worked around the clock for about 4 days and filled over 50 filter press loads. (Most normal batches that we treat only require 1 to 2 loads.) Is there an easier way of going about this treatment? Also, in the event of leaks that spill significant amounts of chromium (5,000 ppm) into tanks containing copper and nickel, is there a good method of chromium removal? We have to add sodium metabisulfite, sodium hydrosulfite, and DTC and sometimes still have to run out very slow in order to stay in spec. High levels of chromium get us way behind in the treatment of our other wastes. Do other shops experience these problems? Thanks in advance to any replies. D. Burton, dburton437Qaol.com I don’t know of an easy way to treat chrome. The bisulfite method is probably the least sludge intensive. The problem is that these etches hold a very high concentration of chrome; further, the sludge that they do generate is really gooey glop that is very hard to filter. The only upside is that it is becoming understood that leaks and unnecessary dumps are not affordable, so that whatever it costs to prevent the leaks and unnecessary dumps looks more attractive every day. Ted Mooney, Finishing Technology, N.J., [email protected] SILVER ELECTROFORM I am working on a project that attempts to electroform hollow tapered tubing of various cross sections. The tapering tubes are sections ranging from approximately 8 mm
square to 5 mm diameter. I am hoping to use female mandrels, which will allow me to grow from the “outsidein,” as I care about the surface quality on the outside and not the inside. I am planning to use a long, thin, depleting silver anode running through the center of the tubes. If I am hoping to grow 120 to 140 microns of silver walls for the tubes, am I going to have problems with anode/cathode proximity being so close (of course, presuming that I monitor the growth somehow so that I don’t get a short)? Also, are there silver baths other than cyanide that are as efficient? Thanks for any information/help/pointers that anyone can give. Richard Chan, Richard-at-the-Saints, [email protected] You may be doing the project the hard way! I think you can get a bright, smooth, finish on the outside with an internal mandrel at these thicknesses. There is a world of difference between the worst electroforms you’ve seen and the best that is achievable. If you do use an internal anode, it seems that a stainless steel one might be a much easier way to go. I don’t think there is any reason to worry about close anode-cathode spacing except for short circuits. I don’t personally know of mainstream noncyanide silver plating solutions yet, but a call to the suppliers of precious metal solutions might be worthwhile. Ted Mooney, Finishing Technology, N.J., [email protected] ALUMINUM
CASTING
ALLOYS
AND FINISHES
We have an outdoor application for natural-colored aluminum castings. The exposure will include all types of industrial and seaside areas. With resistance to corrosion primary, which is the best aluminum casting alloy to use? Secondly, what, if any, surface finish should we apply to enhance the corrosion resistance? Thank you for your suggestions in advance. Ken Wetherbee, [email protected] The best surface finish to retain the natural aluminum look and provide good corrosion resistance would probably be sulfuric acid anodizing to a thickness of 18 to 25 micrometers, followed by a steam or boiling water seal. In general, the purer the aluminum, the more uniform and attractive the finish will be, and the better its corrosion resistance. Ted Mooney, Finishing Technology, N.J., [email protected] Ted Mooney Kinnelon, N.J.
is an independent
consulting
engineer
based in
MF
The Chemical Analysis of Electroplating Solutions by T.H. Irvine 182 pages $65.00 Chapters in this work are divided into groups in accordance with the periodic table of elements. Though the procedures arc traditional, theoretical aspects are included with other information. Anyone who studies this book carefully will derive a helpful understanding of what he or she is doing so that wqmted results can be searched out for causes and corrected Send Orders to: METAL FINISHING, 660 White Plains Rd, Tarrytown, NY 10591-5153 For faster service,call (914) 3332578 or FAX your order to (914) 333-2570 All book orders must be prepaid. NY, NJ and MA residents add appropriate salts tax. Pluse include 15.00 shipping book Air Parcel Port shipment to Canah; and $20.00 for Air Parcel Post shipment to all other countries.
44
and handling
for delivery of each book via UPS to addresses in the U.S.; IS.00 for each
METAL FINISHING
. JUNE 1996
Contact us at http://www.finishing.com/letters
A
s you can see, we now include the E-mail addresses of the participants in the Hotline discussions so that readers can respond immediately and directly to any of the inquiries here; I would appreciate if you would copy [email protected] on any such direct responses. If you’re not using E-mail yet, do yourself the favor of looking into it today. Once you’ve used it, you’ll never go back to time-consuming letters and faxes except when you absolutely must; E-mail is not only faster, easier, less intrusive, and much less expensive, but, with a properly set-up E-mail account, you’ll automatically have a smooth efficient filing system that lets you easily find and review any letter you have ever sent or received. We’ve mentioned several times in recent months that Internet usage is growing explosively. One piece of fallout, though, is that traffic on dial-up BBS’s is drying up to the extent that they no longer have critical mass. Consequently, at about the time you read this, we will be pulling the plug on the BBS; so we ask you to use Internet access exclusively. The World Wide Web address of the Hotline is http://www.finishing.com/letters.
SUBSTITUTES
FOR MEK
Can anyone identify/reference products and companies that can substitute for methyl ethyl ketone (MEK)? The application is our paint booth clean-up. We need to clean the pipes, equipment, and other items and would like to eliminate the use of MEK. Dave Reim, Tech Resources Inc., 75430.53 [email protected] I don’t do industrial painting for a living but have had experience through the years analyzing paints, as well as trying to strip them. There are a number of ways to remove paint, depending upon what the paint is and what the paint is on. Start with contacting the paint supplier and asking for answers. Some of the nonflammable solvents that would work the best are either restricted (l,l, 1-trichloroethane) or carcinogenic (trichloroethylene, methylene chloride). Others are flammable (acetone), flammable and carcinogenic (toluene), or flammable and otherwise toxic (butyl cellosolve). There are the caustic-type strippers based upon sodium hydroxide that don’t dissolve but actually chemically destroy the paint (saponification). You can bum off the paint in a furnace, or use a molten salt bath to do the same thing. Finally, you can blast off the paint using walnut shells or other media in a “sandblaster.” No matter what route you follow, you end up with a potentially hazardous waste. Be METAL FINISHING
??
JULY 1996
0 Copyright
sure to check with your local regulatory agencies before trying to get rid of the final cleanup byproducts. Bill Vins, [email protected] For further options for stripping, case on page 23.
see the Product Show-
FILTER PRESS FOR WASTEWATER
TREATMENT
We have started running a filter press on our pH adjusted wastewater, containing mostly nickel. At pH about 10.5 to 11 .O, we form a decent amount of precipitate, which sort of goes through the filter-press cloth instead of staying on it. Is there a particular cloth weight/density, or whatever measure is commonly applied here, that works well on hydroxides, or would it be advisable to use a filter aid, flocculent, or some other technique to prevent the breakthrough? Berl Stein, b.stein3Qgenie.geis.com I think you need to generate a larger particle size. The filter press cloth is probably quite coarse and most unflocculated metal hydroxides are pretty fine. You should be able to see the floes form as the flocculating agent mixes in. Just don’t overdose, as it will turn the sludge into a slimy mess. Almost any industrial chemical supplier can provide the flocculating agent, probably an anionic agent will work best. Do a jar test first (waste sample in beaker, very small amount of agent added per manufacturer’s dosing rates, mix, and voila-flocculated sludge). Jar tests are good for evaluating different types/manufacturers. You may even get enough in the samples to do the whole job! Bill Vins, [email protected] With regard to the nickel hydroxide precipitate, I would definitely use a filter aid, such as diatomaceous earth, to precoat the cloth. This should prevent leak-through of the precipitate. Rocky C. Costello, PE, [email protected] I’ve used filter presses without filter aid in batch treatment of cleaner dumps, acid dips, and chromates many times and found that the suspended solids slipping through the press were always lower than the suspended solids coming out of the clarifier-such that it didn’t make sense to steer the effluent back through the clarifier and “ruin it.” But in treating a dilute stream, the coarse-woven polypropylene cloth is apparently insufficient. I’ve seen, but haven’t used, a molded membrane-type filter cloth that is very
Elsevier Science Inc.
smooth and shiny on one side, with a heavy flocked finish on the other side; it may be Tyvek. The strange thing is that the vendor didn’t seem to know quite what it is, or even whether the shiny side or flocked side is intended to face out as the filtering surface. If anybody has used such a product, or knows knowledgeable sources for it, I’d like to hear from them. Ted Mooney, Finishing Technology, N.J., [email protected] BATCH TREATMENT
OF CHROMIC
ACID WASTE
I was recently involved in the treatment of a batch of chromium. I work in the waste treatment department of a shop that does electroless plating on plastics. We had some chromic acid, which we use to “rough up” the parts that are plated with copper and nickel. We put about 500 gal or so of this chromic acid in our 3,000-gal batch tank. We had around 47,000 ppm chromium in this batch. We ended up having to treat this batch with about 2,500 lb of sodium metabisulfite. We worked around the clock for about 4 days and filled over 50 filter press loads. (Most normal batches that we treat only require 1 to 2 loads.) Is there an easier way of going about this treatment? Also, in the event of leaks that spill significant amounts of chromium (5,000 ppm) into tanks containing copper and nickel, is there a good method of chromium removal? We have to add sodium metabisulfite, sodium hydrosulfite, and DTC and sometimes still have to run out very slow in order to stay in spec. High levels of chromium get us way behind in the treatment of our other wastes. Do other shops experience these problems? Thanks in advance to any replies. D. Burton, dburton437Qaol.com I don’t know of an easy way to treat chrome. The bisulfite method is probably the least sludge intensive. The problem is that these etches hold a very high concentration of chrome; further, the sludge that they do generate is really gooey glop that is very hard to filter. The only upside is that it is becoming understood that leaks and unnecessary dumps are not affordable, so that whatever it costs to prevent the leaks and unnecessary dumps looks more attractive every day. Ted Mooney, Finishing Technology, N.J., [email protected] SILVER ELECTROFORM I am working on a project that attempts to electroform hollow tapered tubing of various cross sections. The tapering tubes are sections ranging from approximately 8 mm
square to 5 mm diameter. I am hoping to use female mandrels, which will allow me to grow from the “outsidein,” as I care about the surface quality on the outside and not the inside. I am planning to use a long, thin, depleting silver anode running through the center of the tubes. If I am hoping to grow 120 to 140 microns of silver walls for the tubes, am I going to have problems with anode/cathode proximity being so close (of course, presuming that I monitor the growth somehow so that I don’t get a short)? Also, are there silver baths other than cyanide that are as efficient? Thanks for any information/help/pointers that anyone can give. Richard Chan, Richard-at-the-Saints, [email protected] You may be doing the project the hard way! I think you can get a bright, smooth, finish on the outside with an internal mandrel at these thicknesses. There is a world of difference between the worst electroforms you’ve seen and the best that is achievable. If you do use an internal anode, it seems that a stainless steel one might be a much easier way to go. I don’t think there is any reason to worry about close anode-cathode spacing except for short circuits. I don’t personally know of mainstream noncyanide silver plating solutions yet, but a call to the suppliers of precious metal solutions might be worthwhile. Ted Mooney, Finishing Technology, N.J., [email protected] ALUMINUM
CASTING
ALLOYS
AND FINISHES
We have an outdoor application for natural-colored aluminum castings. The exposure will include all types of industrial and seaside areas. With resistance to corrosion primary, which is the best aluminum casting alloy to use? Secondly, what, if any, surface finish should we apply to enhance the corrosion resistance? Thank you for your suggestions in advance. Ken Wetherbee, [email protected] The best surface finish to retain the natural aluminum look and provide good corrosion resistance would probably be sulfuric acid anodizing to a thickness of 18 to 25 micrometers, followed by a steam or boiling water seal. In general, the purer the aluminum, the more uniform and attractive the finish will be, and the better its corrosion resistance. Ted Mooney, Finishing Technology, N.J., [email protected] Ted Mooney Kinnelon, N.J.
is an independent
consulting
engineer
based in
MF
The Chemical Analysis of Electroplating Solutions by T.H. Irvine 182 pages $65.00 Chapters in this work are divided into groups in accordance with the periodic table of elements. Though the procedures arc traditional, theoretical aspects are included with other information. Anyone who studies this book carefully will derive a helpful understanding of what he or she is doing so that wqmted results can be searched out for causes and corrected Send Orders to: METAL FINISHING, 660 White Plains Rd, Tarrytown, NY 10591-5153 For faster service,call (914) 3332578 or FAX your order to (914) 333-2570 All book orders must be prepaid. NY, NJ and MA residents add appropriate salts tax. Pluse include 15.00 shipping book Air Parcel Port shipment to Canah; and $20.00 for Air Parcel Post shipment to all other countries.
44
and handling
for delivery of each book via UPS to addresses in the U.S.; IS.00 for each
METAL FINISHING
. JUNE 1996