- Email: [email protected]
Heard on the hotline
Heardon the Hotline by Ted Mooney, P.E.
Join us at http://www.finishing.cornlLetters
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ast month we printed a thread of conversation regarding estimating air emissions from plating tanks. Let’s start with a follow-up letter that is a critical addition to that thread.
Practice,” third edition or later. McGraw-Hill is another source (this is an extremely old book). I hope you are aware that dry or very nearly dry picric acid is an explosive, War I and II vintage. James Watts, James Watts Inc., [email protected]
ESTIMATING
I searched your discussion about picric acid by browsing the net. I have about 200 grams of picric acid to dispose of. It is currently rendered relatively safe by dissolving it all in several volumes of cold water. The solution will be packed in plastic bottles and sealed before being passed over to the waste disposal contractors. The question I would like to ask is what do tiny crystals of picric acid “explosion” look like. I do not consider myself complacent, but I am sure the vast majority of people working with picric acid have never seen it explode or catch fire because we all sensibly take the advised precautions. My intrigue is that small jars of sodium azide, even picric acid are found on lab benches, usually double contained in another jar. But I have never come across any of them “exploding,” ever. I look forward to your comments. Jayesh Gor, Royal Free Medical School, [email protected]
AIR EMISSIONS
EPA publishes the AP-42 emission factors guidance document for many types of emissions. For nickel plating use Section 12.20 Electroplating Table 2.19. For the clean and etch operations emissions are only considered significant if the tanks are air sparged. In that case use equation 3 in Section 12.20 for estimating uncontrolled emissions due to air sparging. Chem film is usually ambient temperature so there are no emissions. You can find the AP-42 emission factors at http://ttnwww.rtpnc.epa.gov/ Scott Fetter, [email protected] Thanks for the great information. This is exactly what I and the others were looking for. I tried the address and I see that they’ve moved the site to http://www.epa.gov/ttn. I don’t know if it’s an exceptionally busy place or what but the night I called response was so agonizingly slow (79 bytes per second) that navigating the site was impractical. So I’m taking the liberty of providing the complete address, direct to the AP-42 emission factors page: http://www.epa.gov/ttn/chief/ap42etc.html Ted Mooney, Finishing Technology, [email protected]
PICRIC ACID REPLACEMENTS We use minor amounts of picric acid (trinitrophenol) as an etchant prior to nondestructive testing (NDT). We are looking for a replacement for this. I am aware that hydrochloric (muriatic) acid is used as an etchant on concrete. Any experience with hydrochloric acid in NDT work? Is there other possible replacement for picric acid, regardless of use? Any help would be appreciated. Tim Dunn, Portsmouth Naval Shipyard, [email protected] The best list of micro- and macroetchants that I have personally seen is in the metallographic preparation manual from a particular company in Michigan that sells metallographic equipment and supplies. E-mail me for the name of the company. An alternative is a metallographic book available from ASM, “Principles of Metallographic Laboratory METAL FINISHING
??
DECEMBER
1997
0 Copyright
Like all other regular explosives, it takes heat and or a shock to detonate. A similar example is nitroglycerine. It can sit in a bottle on the shelf forever and not explode, just do not drop it when it is quite warm. Picric acid in a bomb is used as a detonator. MSDS sheets here in the USA are very strong in cautions of nearly dry material. You can beat it with a hammer when wet and not have a problem. James Watts, James Watts Inc., [email protected] Yes, even in dry form picric acid needs to be provoked into detonation; however, do not overlook the fact that unscrewing the lid to inspect material may cause material in the threaded area to initiate thus exploding the entire contents of the jar. I have chosen to rehydrate through the lid [without opening] using special protection tools that I have developed. It can then be shipped by a licensed hazardous waste hauler in safe condition. Be careful. Matt Balwinski, Commercial Explosives, [email protected] LIFE TESTING OF ELECTROLESS NICKEL PLATING We are using electroless nickel (EN) to plate mild coldrolled steel equipment frames. These frames are complex
Elsevier Science Inc.
49
shapes with a significant amount of welds. We are homing in on a process to control the plating but the management guys want to be assured the plate will last and protect for 10 years. Is there some accelerated life test anyone knows about the we can run that makes some sense? Our user environment is pretty benign. Worst case, assume a poorly controlled computer room. Temperature 28 + 10°C and 40 to 90% relative humidity. Gary Epp, IUA-Tencor, [email protected] All accelerated tests are for corrosion in a specific environment. Salt spray for instance does not prove much and can be manipulated by the testing agency. It does point out, however, gross failure. The packing material has a lot to do with the failure. Fingerprints and other handling after plating will affect time to failure. Abuse will have more to do with it than most other things. The thickness of your EN will be a major factor in how it will stand up. Finally, what statistical reliability are you looking for-l, 2, 3, or more sigma? James Watts, James Watts Inc., [email protected] We also plate EN and have gone through similar situations of how long the coating will last. For our high-
corrosion finish we apply a high phosphorus EN followed by a chromium seal. The thickness also plays a major part. Do not believe what chemical suppliers say when it comes to their particular system giving 1,000 hours. When looking at EN with respect to high corrosion protection or any other property you want, always start with 1.0 mil. Porosity is a major factor on the finished coating, so make sure you do an acid copper test (it shows up any exposed base metal). If cost is a factor I have had good experience plating 0.5 mil but “bumping” the parts for the first 60 seconds. I can have this lower coating thickness go up to 1,400 hours to red rust. Finally, do not expect fast plating rates. We typically plate between 0.25 and 0.3 mil per hour. This reduces porosity and favors the phosphorus content required for corrosion protection. How long will the coating last? Many years ago I had a discussion with a General Motors specification guru. His rule of thumb was that for every year you wanted a part to last on your car, before it rusted, make sure the part tested for 80 hours in neutral salt spray. Ray Delorey, Industrial Processing, [email protected]
Ted Mooney Ihnnelon, N.J.
is an independent
consulting
engineer
based in MF
TECNUIS YOURSOURCE FOR RECTIFIERS
U
:
NEXT GENERATION PRODUCTS BEST-IN-CLASS CUSTOMER SERVICE Precision
DnraPnlse Pulsed Switch~mode
TecNn, the leading Supplier of Next Generation rectifiers
Circle 067 on reader information card 50
METAL FINISHING
.
DECEMBER
1997
Join us at http://www.finishing.cornlLetters
L
ast month we printed a thread of conversation regarding estimating air emissions from plating tanks. Let’s start with a follow-up letter that is a critical addition to that thread.
Practice,” third edition or later. McGraw-Hill is another source (this is an extremely old book). I hope you are aware that dry or very nearly dry picric acid is an explosive, War I and II vintage. James Watts, James Watts Inc., [email protected]
ESTIMATING
I searched your discussion about picric acid by browsing the net. I have about 200 grams of picric acid to dispose of. It is currently rendered relatively safe by dissolving it all in several volumes of cold water. The solution will be packed in plastic bottles and sealed before being passed over to the waste disposal contractors. The question I would like to ask is what do tiny crystals of picric acid “explosion” look like. I do not consider myself complacent, but I am sure the vast majority of people working with picric acid have never seen it explode or catch fire because we all sensibly take the advised precautions. My intrigue is that small jars of sodium azide, even picric acid are found on lab benches, usually double contained in another jar. But I have never come across any of them “exploding,” ever. I look forward to your comments. Jayesh Gor, Royal Free Medical School, [email protected]
AIR EMISSIONS
EPA publishes the AP-42 emission factors guidance document for many types of emissions. For nickel plating use Section 12.20 Electroplating Table 2.19. For the clean and etch operations emissions are only considered significant if the tanks are air sparged. In that case use equation 3 in Section 12.20 for estimating uncontrolled emissions due to air sparging. Chem film is usually ambient temperature so there are no emissions. You can find the AP-42 emission factors at http://ttnwww.rtpnc.epa.gov/ Scott Fetter, [email protected] Thanks for the great information. This is exactly what I and the others were looking for. I tried the address and I see that they’ve moved the site to http://www.epa.gov/ttn. I don’t know if it’s an exceptionally busy place or what but the night I called response was so agonizingly slow (79 bytes per second) that navigating the site was impractical. So I’m taking the liberty of providing the complete address, direct to the AP-42 emission factors page: http://www.epa.gov/ttn/chief/ap42etc.html Ted Mooney, Finishing Technology, [email protected]
PICRIC ACID REPLACEMENTS We use minor amounts of picric acid (trinitrophenol) as an etchant prior to nondestructive testing (NDT). We are looking for a replacement for this. I am aware that hydrochloric (muriatic) acid is used as an etchant on concrete. Any experience with hydrochloric acid in NDT work? Is there other possible replacement for picric acid, regardless of use? Any help would be appreciated. Tim Dunn, Portsmouth Naval Shipyard, [email protected] The best list of micro- and macroetchants that I have personally seen is in the metallographic preparation manual from a particular company in Michigan that sells metallographic equipment and supplies. E-mail me for the name of the company. An alternative is a metallographic book available from ASM, “Principles of Metallographic Laboratory METAL FINISHING
??
DECEMBER
1997
0 Copyright
Like all other regular explosives, it takes heat and or a shock to detonate. A similar example is nitroglycerine. It can sit in a bottle on the shelf forever and not explode, just do not drop it when it is quite warm. Picric acid in a bomb is used as a detonator. MSDS sheets here in the USA are very strong in cautions of nearly dry material. You can beat it with a hammer when wet and not have a problem. James Watts, James Watts Inc., [email protected] Yes, even in dry form picric acid needs to be provoked into detonation; however, do not overlook the fact that unscrewing the lid to inspect material may cause material in the threaded area to initiate thus exploding the entire contents of the jar. I have chosen to rehydrate through the lid [without opening] using special protection tools that I have developed. It can then be shipped by a licensed hazardous waste hauler in safe condition. Be careful. Matt Balwinski, Commercial Explosives, [email protected] LIFE TESTING OF ELECTROLESS NICKEL PLATING We are using electroless nickel (EN) to plate mild coldrolled steel equipment frames. These frames are complex
Elsevier Science Inc.
49
shapes with a significant amount of welds. We are homing in on a process to control the plating but the management guys want to be assured the plate will last and protect for 10 years. Is there some accelerated life test anyone knows about the we can run that makes some sense? Our user environment is pretty benign. Worst case, assume a poorly controlled computer room. Temperature 28 + 10°C and 40 to 90% relative humidity. Gary Epp, IUA-Tencor, [email protected] All accelerated tests are for corrosion in a specific environment. Salt spray for instance does not prove much and can be manipulated by the testing agency. It does point out, however, gross failure. The packing material has a lot to do with the failure. Fingerprints and other handling after plating will affect time to failure. Abuse will have more to do with it than most other things. The thickness of your EN will be a major factor in how it will stand up. Finally, what statistical reliability are you looking for-l, 2, 3, or more sigma? James Watts, James Watts Inc., [email protected] We also plate EN and have gone through similar situations of how long the coating will last. For our high-
corrosion finish we apply a high phosphorus EN followed by a chromium seal. The thickness also plays a major part. Do not believe what chemical suppliers say when it comes to their particular system giving 1,000 hours. When looking at EN with respect to high corrosion protection or any other property you want, always start with 1.0 mil. Porosity is a major factor on the finished coating, so make sure you do an acid copper test (it shows up any exposed base metal). If cost is a factor I have had good experience plating 0.5 mil but “bumping” the parts for the first 60 seconds. I can have this lower coating thickness go up to 1,400 hours to red rust. Finally, do not expect fast plating rates. We typically plate between 0.25 and 0.3 mil per hour. This reduces porosity and favors the phosphorus content required for corrosion protection. How long will the coating last? Many years ago I had a discussion with a General Motors specification guru. His rule of thumb was that for every year you wanted a part to last on your car, before it rusted, make sure the part tested for 80 hours in neutral salt spray. Ray Delorey, Industrial Processing, [email protected]
Ted Mooney Ihnnelon, N.J.
is an independent
consulting
engineer
based in MF
TECNUIS YOURSOURCE FOR RECTIFIERS
U
:
NEXT GENERATION PRODUCTS BEST-IN-CLASS CUSTOMER SERVICE Precision
DnraPnlse Pulsed Switch~mode
TecNn, the leading Supplier of Next Generation rectifiers
Circle 067 on reader information card 50
METAL FINISHING
.
DECEMBER
1997