- Email: [email protected]
Iron phosphate as a friction surface
lron Phosphate
as a Friction Surface
By Ron Joseph, Organic Coatings Editor
~ : We apply a phosphate coating to the inside and outside of steel tubes. The external surface receives a PTFE electrocoating, but we need to insert a bearing on the inside of the tube. The problem is that when we press the bearing into the tube, the friction force between the bearing and the steel is at our upper specification limit. To reduce the friction, can we apply a dry film lubricant over the phosphate? A : The phosphate coating is microscopically thin, and, if you are using an iron phosphate, then it is thinner than a zinc phosphate. Without conducting laboratory tests in a mechanical test laboratory, I cannot confirm that the application of a dry film lubricant is a good solution. A common problem with friction-fit surfaces is that, over a period of time, the coating might degrade or shrink, in which case the bearing can come loose. I don't know if this is the case with phosphate coatings, but, by applying yet another coating (the dry film lubricant) over the phosphate, in my opinion, you complicate the issue and open yourself to more vulnerability. Rather, you might consider removing the phosphate on the inside or plugging the end of the tubes before they go into the phosphate bath. I assume you have already considered the latter. Acidic solutions are available for dissolving the phosphate, and your chemical supplier can provide you with the appropriate formulation. If you decide to pursue your idea of applying a dry film lubricant, I strongly suggest that you first conduct extensive laboratory tests u n d e r a range of environmental conditions to satisfy y o u r s e l f that the bearing will not loosen with time. F~@EP~L STANDAR@ 5 9 5 B
~ : Does Federal Standard 595B only pertain to wet paint applications or both wet and dry (powder coat) paints? Does it place limits on the amount of lead in the paint? A : F e d e r a l S t a n d a r d 595b colors are u n i v e r s a l and do not apply to a specific type of paint, ink, textile, or anything. It is simply a s t a n d a r d by which anyone can specify a color that he/she would like matched. Although the universe of colors and 48
s h a d e s is infinite, F e d e r a l S t a n d a r d 595b only comprises several hundred. This is not the only color s t a n d a r d available. For instance, the E u r o p e a n s use the RAL color standard, and perhaps other countries have their own standards. Federal S t a n d a r d 595b was developed so t h a t the U.S. g o v e r n m e n t can order colors for g o v e r n m e n t contracts. Of course, architects and o t h e r s doing n o n g o v e r n m e n t w o r k can and do develop and specify any color t h e y choose. The color s t a n d a r d is i n d e p e n d e n t of t h e pigments used in paint, ink, textile, and other industries, therefore, lead-containing p i g m e n t s might not be present. Other regulations limit the amount of lead that a coating can contain, b u t that is independent of Federal S t a n d a r d 595b. ~ E E T | N G F|RE P n O T E C T | @ N D E M A N D S A P O W D E R ©@ATJN@ B@@TH
F@R
~: What are the requirements for automatic sprinkler system protection in powder coating applications? The NFPA is somewhat evasive but seems to treat the requirements the same as solvent-based liquid spray painting.
A : I tend to follow the NFPA recommendations and OSHA requirements. I have not read what OSHA says but I always caution my clients that for insurance purposes, in m y opinion, it is wise to follow existing guidelines and not adopt one of your own. Since you didn't give me the motive for your question, I assume from your company affiliation that you might be an insurance underwriter looking at the risks associated with less fire protection for powders than for liquid coatings. While the risks of fire in a liquid coating facility are predominantly due to the use of flammable solvents, the risks in a powder coating booth are due to electrostatically charged dust particles. Unfortunately, I can't comment on these two very different risk factors, b u t you might w a n t to contact the Powder Coating Institute (www.powdercoating.org) for more information. DETERM|I~|NG THE BRY FI~EM TH|CKNESS @F ~ @ R G A N | C 23NC RJ©H P R I ~ E R
Q: Is it true that the dry film thickness (DFT) per www.metalfinishing.com
coat of solvent-base inorganic zinc shall not exceed 60 microns to maintain the life of paint? We have used solvent-based inorganic zinc paint primer for a heat recovery system gas turbine stack, which will be exposed with a m i n i m u m operating ternperature of 200°C and a m a x i m u m temperature of 285°C. Then we have applied modified silicon acrylic on top of it with a different manufacturer of the primer. The D F T of primer coat is around 150 to 185 microns (5.9-7.3 mils), while the modified silicon acrylic is around 30 to 50 microns (1.2-2.0 mils). A : Zinc rich inorganic primers contain very little resin to hold the zinc particles together. Therefore, it is not advisable to apply too thick a coating, or else you might lose cohesion w i t h i n the coating itself, and the coating might split. Moreover, the coating is not flexible and at high film thickness might crack. This is especially t r u e if the m e t a l surface is h e a t e d and cooled frequently, resulting in cycles of expansion and contraction. The most common r a n g e of film t h i c k n e s s for inorganic zinc rich primers is 75 to 100 microns (3.0-4.0 mils). By applying 150 to 185 microns of the zinc rich primer, you are not getting more corrosion resistance nor, in my opinion, are you getting better h e a t resistance. Again, in my opinion, you are solely adding to the cost of the primer. The DFT of the modified silicon acrylic seems to be in the correct range, but 30 microns might be a bit too low. ©AL©ULt&T|~IG V@© ©OMPL|A~CE FOR N&VY AmTENNAS
Q: I provide oversight on contractors" resurfacing of antenna arrays. I u n d e r s t a n d that when the contractor resurfaces an antenna he has to certify that the VOC content of the products he uses is less than or equal to the Federal VOC content (530 g / L for antennas). The contractor uses xylene to solvent clean the surfaces. Xylene's VOC is over 530 g / L ; it's 875 g / L . The contractor also uses a primer that's over the 530- g / L limit. My question is how is this in compliance? Is it because the solvent cleaner is not considered a part of the coating? What about the primer? They only use 1.125 pints of primer per antenna. Does this allow it to be used? A : Unfortunately, I do not know to which regulation you are referring; therefore, I can't give you a direct answer. In most regulations, the solvent used to prepare the metal surface is not included in the calcu-
lation of VOC for the coating. On the other hand, if the paint is thinned with the solvent, then the calculation does include the solvent. In the regulation to which you are referring, the xy]ene might not be regulated, since, according to what you wrote, it is used solely to prepare the surfaces. If the primer has a VOC that is outside the limit of the regulation, then your assumption that it is out of compliance is correct. You need to see if the regulation has separate values for primer and topcoat. Finally, m a n y regulations exempt low-quantity usage. This can be b a s e d on a daily, monthly, or annual basis, and you will need to read the regulation to see if the contractor falls into such an exemption. If the contractor uses 1.125 pints of coating per antenna, b u t refurbishes 100 antennas, t h e n the coating usage is no longer a small quantity. I hope this helps, but, without actually seeing the specific regulation to which you are referring, I cannot help you further. Ron Joseph is an independent coating consultant in San Jose, Calif. You can e-mail questions to [email protected], ln~
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A corporate sale is a complex task. Our street-smart entrepreneurial approach guides you through the entire process. We are experienced, seasoned professionals, who successfully complete more acquisitions per person than any other firm. M y company negotiates a transaction structure that p r o t e c t s o u r c l i e n t s from post-closing litigation. For additional information about our unique services, contact:
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301, 4284
Allison 412/486-8189
Park,
• email:
Route
8
PA 15101 [email protected]
www.georgespilka.com Circle 001 on reader informationcard or go to www.metalfinishing.com/advertisers
October 2005
49
as a Friction Surface
By Ron Joseph, Organic Coatings Editor
~ : We apply a phosphate coating to the inside and outside of steel tubes. The external surface receives a PTFE electrocoating, but we need to insert a bearing on the inside of the tube. The problem is that when we press the bearing into the tube, the friction force between the bearing and the steel is at our upper specification limit. To reduce the friction, can we apply a dry film lubricant over the phosphate? A : The phosphate coating is microscopically thin, and, if you are using an iron phosphate, then it is thinner than a zinc phosphate. Without conducting laboratory tests in a mechanical test laboratory, I cannot confirm that the application of a dry film lubricant is a good solution. A common problem with friction-fit surfaces is that, over a period of time, the coating might degrade or shrink, in which case the bearing can come loose. I don't know if this is the case with phosphate coatings, but, by applying yet another coating (the dry film lubricant) over the phosphate, in my opinion, you complicate the issue and open yourself to more vulnerability. Rather, you might consider removing the phosphate on the inside or plugging the end of the tubes before they go into the phosphate bath. I assume you have already considered the latter. Acidic solutions are available for dissolving the phosphate, and your chemical supplier can provide you with the appropriate formulation. If you decide to pursue your idea of applying a dry film lubricant, I strongly suggest that you first conduct extensive laboratory tests u n d e r a range of environmental conditions to satisfy y o u r s e l f that the bearing will not loosen with time. F~@EP~L STANDAR@ 5 9 5 B
~ : Does Federal Standard 595B only pertain to wet paint applications or both wet and dry (powder coat) paints? Does it place limits on the amount of lead in the paint? A : F e d e r a l S t a n d a r d 595b colors are u n i v e r s a l and do not apply to a specific type of paint, ink, textile, or anything. It is simply a s t a n d a r d by which anyone can specify a color that he/she would like matched. Although the universe of colors and 48
s h a d e s is infinite, F e d e r a l S t a n d a r d 595b only comprises several hundred. This is not the only color s t a n d a r d available. For instance, the E u r o p e a n s use the RAL color standard, and perhaps other countries have their own standards. Federal S t a n d a r d 595b was developed so t h a t the U.S. g o v e r n m e n t can order colors for g o v e r n m e n t contracts. Of course, architects and o t h e r s doing n o n g o v e r n m e n t w o r k can and do develop and specify any color t h e y choose. The color s t a n d a r d is i n d e p e n d e n t of t h e pigments used in paint, ink, textile, and other industries, therefore, lead-containing p i g m e n t s might not be present. Other regulations limit the amount of lead that a coating can contain, b u t that is independent of Federal S t a n d a r d 595b. ~ E E T | N G F|RE P n O T E C T | @ N D E M A N D S A P O W D E R ©@ATJN@ B@@TH
F@R
~: What are the requirements for automatic sprinkler system protection in powder coating applications? The NFPA is somewhat evasive but seems to treat the requirements the same as solvent-based liquid spray painting.
A : I tend to follow the NFPA recommendations and OSHA requirements. I have not read what OSHA says but I always caution my clients that for insurance purposes, in m y opinion, it is wise to follow existing guidelines and not adopt one of your own. Since you didn't give me the motive for your question, I assume from your company affiliation that you might be an insurance underwriter looking at the risks associated with less fire protection for powders than for liquid coatings. While the risks of fire in a liquid coating facility are predominantly due to the use of flammable solvents, the risks in a powder coating booth are due to electrostatically charged dust particles. Unfortunately, I can't comment on these two very different risk factors, b u t you might w a n t to contact the Powder Coating Institute (www.powdercoating.org) for more information. DETERM|I~|NG THE BRY FI~EM TH|CKNESS @F ~ @ R G A N | C 23NC RJ©H P R I ~ E R
Q: Is it true that the dry film thickness (DFT) per www.metalfinishing.com
coat of solvent-base inorganic zinc shall not exceed 60 microns to maintain the life of paint? We have used solvent-based inorganic zinc paint primer for a heat recovery system gas turbine stack, which will be exposed with a m i n i m u m operating ternperature of 200°C and a m a x i m u m temperature of 285°C. Then we have applied modified silicon acrylic on top of it with a different manufacturer of the primer. The D F T of primer coat is around 150 to 185 microns (5.9-7.3 mils), while the modified silicon acrylic is around 30 to 50 microns (1.2-2.0 mils). A : Zinc rich inorganic primers contain very little resin to hold the zinc particles together. Therefore, it is not advisable to apply too thick a coating, or else you might lose cohesion w i t h i n the coating itself, and the coating might split. Moreover, the coating is not flexible and at high film thickness might crack. This is especially t r u e if the m e t a l surface is h e a t e d and cooled frequently, resulting in cycles of expansion and contraction. The most common r a n g e of film t h i c k n e s s for inorganic zinc rich primers is 75 to 100 microns (3.0-4.0 mils). By applying 150 to 185 microns of the zinc rich primer, you are not getting more corrosion resistance nor, in my opinion, are you getting better h e a t resistance. Again, in my opinion, you are solely adding to the cost of the primer. The DFT of the modified silicon acrylic seems to be in the correct range, but 30 microns might be a bit too low. ©AL©ULt&T|~IG V@© ©OMPL|A~CE FOR N&VY AmTENNAS
Q: I provide oversight on contractors" resurfacing of antenna arrays. I u n d e r s t a n d that when the contractor resurfaces an antenna he has to certify that the VOC content of the products he uses is less than or equal to the Federal VOC content (530 g / L for antennas). The contractor uses xylene to solvent clean the surfaces. Xylene's VOC is over 530 g / L ; it's 875 g / L . The contractor also uses a primer that's over the 530- g / L limit. My question is how is this in compliance? Is it because the solvent cleaner is not considered a part of the coating? What about the primer? They only use 1.125 pints of primer per antenna. Does this allow it to be used? A : Unfortunately, I do not know to which regulation you are referring; therefore, I can't give you a direct answer. In most regulations, the solvent used to prepare the metal surface is not included in the calcu-
lation of VOC for the coating. On the other hand, if the paint is thinned with the solvent, then the calculation does include the solvent. In the regulation to which you are referring, the xy]ene might not be regulated, since, according to what you wrote, it is used solely to prepare the surfaces. If the primer has a VOC that is outside the limit of the regulation, then your assumption that it is out of compliance is correct. You need to see if the regulation has separate values for primer and topcoat. Finally, m a n y regulations exempt low-quantity usage. This can be b a s e d on a daily, monthly, or annual basis, and you will need to read the regulation to see if the contractor falls into such an exemption. If the contractor uses 1.125 pints of coating per antenna, b u t refurbishes 100 antennas, t h e n the coating usage is no longer a small quantity. I hope this helps, but, without actually seeing the specific regulation to which you are referring, I cannot help you further. Ron Joseph is an independent coating consultant in San Jose, Calif. You can e-mail questions to [email protected], ln~
Selling Your Company... • • • •
All Cash Deals Premium Prices Obtained Negotiating Power Personalized, Tailored Service
A corporate sale is a complex task. Our street-smart entrepreneurial approach guides you through the entire process. We are experienced, seasoned professionals, who successfully complete more acquisitions per person than any other firm. M y company negotiates a transaction structure that p r o t e c t s o u r c l i e n t s from post-closing litigation. For additional information about our unique services, contact:
D
GEORGE SPILKAAND ASSOCIATES Merger & Acquisition Consultants Suite
301, 4284
Allison 412/486-8189
Park,
• email:
Route
8
PA 15101 [email protected]
www.georgespilka.com Circle 001 on reader informationcard or go to www.metalfinishing.com/advertisers
October 2005
49