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Environmental coating problems
Environmental Problems
Coating
by Ron Joseph
Use the Shop Problem Card
Paint Liners Versus Nonstick Coatings for Pressure Pots The following letter was recently sent to me by a good friend, Dean Cornstubble of Research Triangle Institute in North Carolina: Paint liners are a good idea for those who are willing to spend the time inserting, removing, and cleaning them in a production setting. Is this always going to be the case’?Highly unlikely. Folks tend to get careless when they have routine monotonous jobs to perform day-in and day-out. I think nonstick coatings offer the user an advantage by providing a contact surface that is inert to the contacting fluid. Thus, gravity draining, air blowdown, or minimal wiping become much less labor intensive and force the line worker to “accept” the fact that the area they used to clean on a routine basis is no longer necessary. Economically. it makes sense. Now, there are three ma.jor problems with the use of nonstick coatings in manufacturing settings: inertness to the contacting fluid. downtime for customcoating individual parts, and nonstick coating degradation. Inertness to the contacting fluid is extremely important since you don’t want the contacting fluid to attack the nonstick coating. Downtime of a process will be a critical business decision for small businesses due to the fact that they cannot afford to be down for very long for custom coating. Degradation of the nonstick coating is by far the most important factor and for which we hope to secure funding to investigate further. The project I am working on is focused on demonstration of the use of the technology and not to investigate the duration and effects of wear and tear of the nonstick coatings in service. D.C. During the past many years I have visited several paint facilities where METAL FINISHING . NOVEMBER 1998
in this
issue
fix
free
expert
advice
the painters have inserted plastic liners into pressure pots as a pollution-prevention strategy and this is now their rnodus operandi. The procedure is quick and couldn’t be easier to perform. Old paint is wiped off the plastic surface using a solvent-laden rag, or if the paint has already hardened, a little flexing of the plastic causes the old dry paint simply to flake off; therefore, the procedure is not time consuming and I don’t know why painters would not continue doing this ad infinitum. After all, it is cleaner (for the painter) to use the liners than to clean out the pressure pot itself, as in the past. When the line1 becomes old and damaged it can be disposed of in the dumpster. Now let us consider the innovative idea of lining the pressure pot with a truly inert coating. as suggested by our contributor. I agree with all of the potential problem areas suggested by him, but for what it’s worth here are some clarifying comments. Inert nonstick coatings. such as nylons, or even the more sophisticated chlorinated-fluorinated coatings, such as Teflon, exist but they are expensive and require excellent surface preparation before being applied; moreover, they usually must be baked at high temperatures, in excess of 400°F. Hence cost is a factor that the contributor did not mention in his list of problem areas. It seems to me that any owner of a paint shop who is interested in purchasing a pressure pot that has been lined with a nonstick coating would build downtime into the equation. For instance, he might purchase an extra pressure pot while still using his existing, uncoated one. When the new one arrives have the old one coated. AS was acknowledged by our contributor. it would seem that coating degradation and physical damage would be the major drawbacks. Phys0 Copyright ElsevrerScience Inc.
ical damage can take place so easily. When the (heavy) head of the pressure pot is lowered onto the pot itself the fluid tube can easily scratch the nonstick lining. Painters are not immune to using screw drivers, wrenches, pliers, wire, and other tools when trying to attach fittings to the spray equipment, pressure regulators. etc., and I would imagine that these can sometimes fall into the pressure pot. As long as the pot is tnade of steel no significant damage occurs. but it the pot were to be lined with a coating then perhaps the damage could be :significant. At some point the owner will need to have the pot abrasive blasled to remove the coating and then apply the coating again. If the nonstick coating is sophisticated, as I suggested earlier, the pressure pot might need to be recoated off-site. Expensive! In summary I think the idea is innovative. but in my opinion the inexpensive plastic liner is hard to beat. Getting a Uniform DFT with a High-Solids Epoxy Primer . We use a high-solids epoxy to . prime over metal surfaces but cannot get a uniform coating of I .O mil; moreover, we have lots of orange peel. which affects the appearance of the topcoat. Do you know of a low-VOC epoxy that will resolve this problem? S.M.W. Apparently. epoxy primers that : comply with Mil-P-53022 have a solids content of approximately 60 to 65% yet exhibit a low viscosity. A friend who has used this coating assures me that you should be able to get a uniform film thickness of I.0 mil. But for those of our readers who are interested in using VOC-compliant epoxy primers. let me also remind you of the waterborne epoxy versions, which meet Mil-P-53030 (nonchromate) and
Q
A
75
Mil-P-85582 (chromate-containing). These waterborne epoxy primers have low solids and low viscosity. In fact, for some formulations, it is often difficult to even get to 1.0 mil without causing the primer to run or sag. Fines for Mixers? Does the individual who mixes : paint incorrectly get the fine if the coating is inspected and tested by the EPA and found to be in violation? C.W.
Q
. If the person who mixes the . paint is diligently following the instructions on the label of the can, or in the company’s procedures manual, I sincerely doubt that he/she would be fined. After all, how would the person know that the VOC content of the coating is in violation of a local regulation? On the other hand, if the person deliberately adds thinners to the coating
A
even though this is contrary to manufacturer’s instructions, the inspector might well be less lenient. In the most likely scenario an inspector takes a sample, sends it to an outside lab for analysis, and, if the VOC is over the limit, issues a Notice of Violation (NOV). The NOV is usually mailed to the environmental contact person rather than to the person who added the thinners. Invariably, some senior official within the company gets to hear of the NOV and then makes inquiries to determine who got the company into the mess; therefore, while the EPA might not take action against the perpetrator, the company official may do so instead. More on Thinning . If the label on a can says “Use . as is- no thinning required,” but the data sheet shows that the VOC
Q
l
l
is less than the regulatory limit, can I add thinners? J.D. . If the VOC of the coating is less . than the regulatory limit. you can add thinners, but bear in mind that when you do so you must be sure that you don’t overshoot the mark. Recently, I was in a paint shop where the painters were told to use the coating as mixed and supplied by the vendor. One of the painters decided that the only way he could eliminate orange peel was to add thinners and he did so without first asking his supervisor or performing simple calculations to confirm compliance. That was a risky move on his part and should an inspector have walked into the shop at that moment, he might have cited the painter directly.
A
Ron Joseph is an independent coating consultant in San Jose, Calif. MF
Precipitates heavy metal ions, forming coarse, easily dewatered, nonleachable flow
l
l
Is an environmentally safe product. exhibiting very low toxicity towards aquatic organisms (fish, shrimp), bacteria, and humans.
l
Works in acidic, neutral, and alkaline media. Does not release toxic gases (e.g., hydrogen sulfide) or flammable, toxic products (e.g.. carbon disulfide), even at pH ~1. Frequently volumes.
reduces
sludge
For more information, call or write to: Eckehart Roland Degussa Corporation 65 Challenger Road Ridgefield Park, NJ 07660 Tel:- (201) 641-6100 Fax: (201) 641-0385
Degussa + Desu= Corporation
Circle
76
138 on reader
information
card
Circle
Visit our Web site at: http:l/www .degussa.com
027 on reader
METAL
information
FINISI-iING
card l
NOVEMBER
1998
Coating
by Ron Joseph
Use the Shop Problem Card
Paint Liners Versus Nonstick Coatings for Pressure Pots The following letter was recently sent to me by a good friend, Dean Cornstubble of Research Triangle Institute in North Carolina: Paint liners are a good idea for those who are willing to spend the time inserting, removing, and cleaning them in a production setting. Is this always going to be the case’?Highly unlikely. Folks tend to get careless when they have routine monotonous jobs to perform day-in and day-out. I think nonstick coatings offer the user an advantage by providing a contact surface that is inert to the contacting fluid. Thus, gravity draining, air blowdown, or minimal wiping become much less labor intensive and force the line worker to “accept” the fact that the area they used to clean on a routine basis is no longer necessary. Economically. it makes sense. Now, there are three ma.jor problems with the use of nonstick coatings in manufacturing settings: inertness to the contacting fluid. downtime for customcoating individual parts, and nonstick coating degradation. Inertness to the contacting fluid is extremely important since you don’t want the contacting fluid to attack the nonstick coating. Downtime of a process will be a critical business decision for small businesses due to the fact that they cannot afford to be down for very long for custom coating. Degradation of the nonstick coating is by far the most important factor and for which we hope to secure funding to investigate further. The project I am working on is focused on demonstration of the use of the technology and not to investigate the duration and effects of wear and tear of the nonstick coatings in service. D.C. During the past many years I have visited several paint facilities where METAL FINISHING . NOVEMBER 1998
in this
issue
fix
free
expert
advice
the painters have inserted plastic liners into pressure pots as a pollution-prevention strategy and this is now their rnodus operandi. The procedure is quick and couldn’t be easier to perform. Old paint is wiped off the plastic surface using a solvent-laden rag, or if the paint has already hardened, a little flexing of the plastic causes the old dry paint simply to flake off; therefore, the procedure is not time consuming and I don’t know why painters would not continue doing this ad infinitum. After all, it is cleaner (for the painter) to use the liners than to clean out the pressure pot itself, as in the past. When the line1 becomes old and damaged it can be disposed of in the dumpster. Now let us consider the innovative idea of lining the pressure pot with a truly inert coating. as suggested by our contributor. I agree with all of the potential problem areas suggested by him, but for what it’s worth here are some clarifying comments. Inert nonstick coatings. such as nylons, or even the more sophisticated chlorinated-fluorinated coatings, such as Teflon, exist but they are expensive and require excellent surface preparation before being applied; moreover, they usually must be baked at high temperatures, in excess of 400°F. Hence cost is a factor that the contributor did not mention in his list of problem areas. It seems to me that any owner of a paint shop who is interested in purchasing a pressure pot that has been lined with a nonstick coating would build downtime into the equation. For instance, he might purchase an extra pressure pot while still using his existing, uncoated one. When the new one arrives have the old one coated. AS was acknowledged by our contributor. it would seem that coating degradation and physical damage would be the major drawbacks. Phys0 Copyright ElsevrerScience Inc.
ical damage can take place so easily. When the (heavy) head of the pressure pot is lowered onto the pot itself the fluid tube can easily scratch the nonstick lining. Painters are not immune to using screw drivers, wrenches, pliers, wire, and other tools when trying to attach fittings to the spray equipment, pressure regulators. etc., and I would imagine that these can sometimes fall into the pressure pot. As long as the pot is tnade of steel no significant damage occurs. but it the pot were to be lined with a coating then perhaps the damage could be :significant. At some point the owner will need to have the pot abrasive blasled to remove the coating and then apply the coating again. If the nonstick coating is sophisticated, as I suggested earlier, the pressure pot might need to be recoated off-site. Expensive! In summary I think the idea is innovative. but in my opinion the inexpensive plastic liner is hard to beat. Getting a Uniform DFT with a High-Solids Epoxy Primer . We use a high-solids epoxy to . prime over metal surfaces but cannot get a uniform coating of I .O mil; moreover, we have lots of orange peel. which affects the appearance of the topcoat. Do you know of a low-VOC epoxy that will resolve this problem? S.M.W. Apparently. epoxy primers that : comply with Mil-P-53022 have a solids content of approximately 60 to 65% yet exhibit a low viscosity. A friend who has used this coating assures me that you should be able to get a uniform film thickness of I.0 mil. But for those of our readers who are interested in using VOC-compliant epoxy primers. let me also remind you of the waterborne epoxy versions, which meet Mil-P-53030 (nonchromate) and
Q
A
75
Mil-P-85582 (chromate-containing). These waterborne epoxy primers have low solids and low viscosity. In fact, for some formulations, it is often difficult to even get to 1.0 mil without causing the primer to run or sag. Fines for Mixers? Does the individual who mixes : paint incorrectly get the fine if the coating is inspected and tested by the EPA and found to be in violation? C.W.
Q
. If the person who mixes the . paint is diligently following the instructions on the label of the can, or in the company’s procedures manual, I sincerely doubt that he/she would be fined. After all, how would the person know that the VOC content of the coating is in violation of a local regulation? On the other hand, if the person deliberately adds thinners to the coating
A
even though this is contrary to manufacturer’s instructions, the inspector might well be less lenient. In the most likely scenario an inspector takes a sample, sends it to an outside lab for analysis, and, if the VOC is over the limit, issues a Notice of Violation (NOV). The NOV is usually mailed to the environmental contact person rather than to the person who added the thinners. Invariably, some senior official within the company gets to hear of the NOV and then makes inquiries to determine who got the company into the mess; therefore, while the EPA might not take action against the perpetrator, the company official may do so instead. More on Thinning . If the label on a can says “Use . as is- no thinning required,” but the data sheet shows that the VOC
Q
l
l
is less than the regulatory limit, can I add thinners? J.D. . If the VOC of the coating is less . than the regulatory limit. you can add thinners, but bear in mind that when you do so you must be sure that you don’t overshoot the mark. Recently, I was in a paint shop where the painters were told to use the coating as mixed and supplied by the vendor. One of the painters decided that the only way he could eliminate orange peel was to add thinners and he did so without first asking his supervisor or performing simple calculations to confirm compliance. That was a risky move on his part and should an inspector have walked into the shop at that moment, he might have cited the painter directly.
A
Ron Joseph is an independent coating consultant in San Jose, Calif. MF
Precipitates heavy metal ions, forming coarse, easily dewatered, nonleachable flow
l
l
Is an environmentally safe product. exhibiting very low toxicity towards aquatic organisms (fish, shrimp), bacteria, and humans.
l
Works in acidic, neutral, and alkaline media. Does not release toxic gases (e.g., hydrogen sulfide) or flammable, toxic products (e.g.. carbon disulfide), even at pH ~1. Frequently volumes.
reduces
sludge
For more information, call or write to: Eckehart Roland Degussa Corporation 65 Challenger Road Ridgefield Park, NJ 07660 Tel:- (201) 641-6100 Fax: (201) 641-0385
Degussa + Desu= Corporation
Circle
76
138 on reader
information
card
Circle
Visit our Web site at: http:l/www .degussa.com
027 on reader
METAL
information
FINISI-iING
card l
NOVEMBER
1998