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Heard on the Hotline
Heard on the Hotline by Ted Mooney, P.E.
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B
ecause most of my personal experience has been with plating and inorganic finishing, we haven't often printed much about painting and organic coatings in this column. But a lot of people have been contributing their expertise in those topics, so I think it's time we gave our readers the benefit of some of those efforts. ALGAE PROBLEMS I am looking for a simple treatment to prevent algae in the anolyte system for electrodeposition. Arie Porat Tzora Furniture, Israel [email protected] Some people have had luck with ultraviolet (UV) light. Some people filter more. One manufacturer recommends an "antiseptic" for their dye solutions. Heating kills most algae, as hot as the solution will tolerate shortens the time. You then have to filter the solution to get the dead stuff out or it messes up the finish on the parts. I have yet to figure out how the stuff can grow in some very noxious solutions. James Watts James Watts Inc. [email protected] How about plating in the dark? I would send some of the bugs to the local agricultural college to determine what you've got growing. Tom Pullizzi Team*Faraday Inc. [email protected] I don't have any experience with anolyte systems, but I just finished reviewing a bunch of earlier letters dealing with years of experience fighting algae/fungus/mold growth in plating rinses. Much of it may be inapplicable because of sensitivity of the anolyte, but it covers a lot of bases and may at least provide food for thought. Some of the proven approaches were: UV light (already mentioned); bleach (cheap, but will it destroy the anolyte?); peroxide and ozone generators (ditto); commercial algaecides for fish tanks, available from pet stores. To complete the list with some "out there" possibilities: potassium permanganate, formaldehyde, copper sulfate, silver nitrate, and potassium chromate. The more I go on, the better the UV is sounding to me. Ted Mooney Finishing Technology [email protected] 56
REMOVING POWDER COATING FROM MAGNESIUM How could one remove the powder coating from the surface of a magnesium wheel in order to polish the wheel? Also, would this be detrimental in any way to the performance of a racing wheel? John Hubbs College Station, Texas [email protected] For your purposes it sounds like the best course of action is to find some place that does plastic media blasting. They can remove the coating without damaging the magnesium and will do them one at a time. Also plastic media will not roughen the surface any further, important since you want to polish it later. Other chemical or mechanical means could either harm the piece or roughen the surface. Craig A. Burkart Texo Corp. [email protected] There are environmentally safe cleaning chemicals that have been found to be extremely aggressive for the removal of powder coatings. As a cold strip, a gel formulation may work well. Fred Wellman WSI Chemical Inc. [email protected] How would Mr. Hubbs decide whether chemically cleaning the wheels himself is more appropriate than finding a shop to do the plastic media blasting? If they were my wheels, I'd take them to a shop and let them make the decision whether to try mechanical or chemical means. Ted Mooney Finishing Technology [email protected]
.
POWDER COATING PRETREATMENT Is iron phosphating the best pretreatment for exterior articles? Are any laser devices or temperature gauging equipment available by which the temperature of any comer of an oven can be measured? Anil Tiwari Phoenix Fabricators, India [email protected]
© Copyright Elsevier Science Inc.
METAL FINISHING. OCTOBER 1998
What is the substrate? Aluminum? For aluminum, yellow chromate conversion coating is the best; however there are new nonchromate coatings claimed equivalent or better than yellow chromate. For steel substrates, I think you are right, iron phosphate is the best. There are several temperature "measuring and recording" instruments that travel with the workpiece in the oven so that you can see the temperature distribution versus time in the oven and of the workpiece itself. I think this is better than measuring the temperature of the oven's atmosphere. Timur Ulucak [email protected] For fear of oversimplifying pretreatment I won't list all the possibilities, but in order to determine what materials and methods of pretreatment to employ, you need to let everyone know the substrate, what conditions it will see, and what type of coating you intend to apply. Jim Cummings Buffalo Powder Coating [email protected]
AUTOPHORETIC COATING PROCESS Has anyone ever used, or does anyone know anything about, the autophoretic coating process? Anybody using it in the Northeast? Thomas Moffitt Mass. Office of Technical Assistance [email protected] Well, you have to remember that it is an organic coating, not a metallurgically bonded electroplating. So, if you want to replace paint, it may be a good fit. We looked at it for some heavy zinc-plated couplings and had to dismiss it because the parts are handled roughly, are used outside, and would chip and rust. Of course, that doesn't mean that all parts will chip and rust! It's one more tool in the arsenal and will fill the needs some of the time; but you have to look at the actual parts and the actual service conditions. Ted Mooney Finishing Technology [email protected]
~'C:,=;r=,c:amgs "I:i'i"':~~ii~{~~~~'I;:II,~I~bUilt)Instruments
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i41t-/ •.
• As£~~jt~~:~~gged, Easy To Use tiibaKrn Program for your old
. . ,.• '•.. •.•.•••••.. . . . .
Gl:lg~§c.mn~~.J?srg'~
Recalibration servi~;~':~::::~;;;'!jl!llii';. Ii ,,-,~swhile yours are se~1II11t :,t ,'I
;;ill ;
•
iii.::.. "lii¥,
by Justech Inc.
:::::::>-:',:::::>:':::.,:.:>:.:.:,.
JUSTECHIN@r{
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METAL FINISHING • OCTOBER 1998
57
A well-known paint manufacturer (name supplied via E-mail) offers their paper "Comprehensive Comparison of Electrocoat vs. Autodeposition." Autodeposition and autophoretic are the same. Tyrone L. Caley Caley & Associates [email protected]
Hmm, does that supplier of electrocoating materials offer autophoretic coatings? If not, I'm not so sure that this work would have legitimate scholarly value. At the least I would want to see it challenged by a supplier of autophoretic coatings before I'd put full credence in its comprehensiveness. Ted Mooney Finishing Technology [email protected]
ADHESION OF LACQUER PAINTS TO SILVER· PLATED OBJECTS I am a fishing lure manufacturer. Getting lacquer paint to stick to silver-plated lures is my problem. Traditional methods are not durable enough. While I do not paint myself, my supplier has attempted to search through the automotive
industry and has come up with a fair product but not the standard I am looking for. Jim Martino Tamiron Sporting Goods Inc [email protected] Silver takes a chromate, not usually useful for silver plate, but usually good for paint adhesion. Is the paint over the entire lure, or only in selected areas? Tom Pullizzi Team*Faraday Inc. [email protected] Per the 1998 edition of the Metal Finishing Organic Finishing Guidebook and Directory, in an article by Earl C. Groshart, Consultant, new silver can be painted immediately following thorough cleaning, preferably vapor degreasing, or may be chromate conversion coated prior to painting. He notes that silver with sulfide tarnish, as long as it's not powdery, will take paint. Mike Moninger Thermospray, Sarasota, Fla. [email protected] We have had success applying lacquer-base paints to metallic surfaces (i.e., boat propellers to prevent algae
Singleton CCTn ChAMbER Introducing the New State ofthe Art
. •.•.•. •• ·~~p.geeaWO ••v..ilabl~···
Re::;~:ee •800428-3502 ..
e-Penonns Cyclic Corrosion Tests ·HowProfile Design for easy access .:.Power Assisted Cover
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58
Circle 070 on reader information card
METAL FINISHING. OCTOBER 1998
growth). We slightly sand the metallic surface, apply a base coat, followed by the paint application, then the protective coating. It has worked for us. Todd Miller Bronze Company II [email protected] PREPARATION OF STAINLESS STEEL FOR EPOXY POWDER COATING
I have a stainless steel enclosure and would like to epoxy powder coat it. What type of surface preparation is required for stainless steel in a powder coat finish application? Christopher Cioccio Union Switch and Signal [email protected] We have pretreated stainless steel with an alkaline cleaner, then either zinc phosphated or chrome phosphated, and painted with a TGIC. We used these chemicals and the painted parts passed the cross-hatch adhesion test. As always, getting the part clean is real important. Also, if the stainless steel mill finish is real smooth, a deoxidizer etch might help. Kelly Loch Carrier Transicol [email protected] Stainless steel does not lend itself to phosphating. I have seen instances where the stainless steel is zinc or cadmium plated and then phosphated. R.Sivakumar [email protected] I agree with the previous message, stainless steel does not accept a zinc phosphate coating. The important factor that you should be looking at is the surface roughness of the stainless steel. A roughened surface will accept paint more readily than a smooth one. In fact one of the ways to prepare stainless steel for painting is to sandblast or roughen the surface after cleaning. A wash primer may also be a way to get the final coat to adhere better. Craig A. Burkart Texo Corp. [email protected] FINISHING WROUGHT IRON FURNITURE
I have started a small company making steel furniture and other items (park benches, tables, etc.) I usually finish with a primer, then Rustoleum. Most of the items are made from hot-rolled steel, and some involve smithing. I've been descaling the steel using muriatic acid then rinsing with a hard stream of water. I can't seem to avoid getting some oxidation during the drying process. Here are my questions: How important is the descaling? How clean does the metal need to be? Am I going about it the right way? Is that little surface rust acceptable, or is there an easy way to eliminate it? (I can't always reach the parts with a wire brush, and that's unproductive). How does large-scale industry do it? How clean is their metal before powder coating, for examMETAL FINISHING • OCTOBER 1998
ple? Are there different kinds of primers? The stuff I'm making is looking good, I just need some guidance about how neurotic to be with the metal preparation. Thanks in advance for those of you willing to share your expertise. Art Thompson Art Works, Harrisonburg, Va. [email protected] Descaling hot-rolled steel is very important because the heat scale does not provide a very good adhesive surface for the coating. You are only missing one thing. A short-term corrosion inhibitor for the rinsewater. Once you have removed the scale, the surface of the steel is very active and will begin to corrode almost instantly because you have left the surface acidic. There are two ways to go here: You can phosphatize the surface with an iron phosphate solution with the pressure washer, or apply an alkaline rust preventive mixed with the rinsewater to prevent flash rusting while the parts dry. Both ways are being used by industrial plants that paint very large items from heavy equipment to dumpsters. Craig A. Burkart Texo Corp. [email protected] A cheap alternative to a phosphate system is to use a mixture of sulfuric and phosphoric acid to remove the scale. A thin layer of iron phosphate on the surface provides short-term protection. Laurence van Niekerk [email protected] I am manufacturing wrought iron furniture from hot-rolled steel (l if2-in. x 1;4.-in. bar stock for example). I have already powder coated some of our items but am not entirely happy with the "look." I would like some suggestions on what to use to finish these items and how to apply it. Greg Klein Loader Ltd., Ontario [email protected] How about a texture/splatter coat? This will hide some minor imperfections. Patrick Langan [email protected] See my question above for related information. I get a nice finish from Rustoleum Outdoor Satin, sprayed with an HVLP sprayer. It has a more natural, hand-painted look than the powder coat. Don't just use the standard black wrought iron look. Experiment with different colors, it will make your work stand out. I also have made some pieces where I polish the steel to a "pewter" look, than clear coat with lacquer. You can't hide any mistakes or slips of the grinder this way, though. Art Thompson Art Works, Harrisonburg, Va. [email protected] Ted Mooney is an independent consulting engineer based in MF Brick, N.J.
59
Join us at http://www.finishing.com/Letters
B
ecause most of my personal experience has been with plating and inorganic finishing, we haven't often printed much about painting and organic coatings in this column. But a lot of people have been contributing their expertise in those topics, so I think it's time we gave our readers the benefit of some of those efforts. ALGAE PROBLEMS I am looking for a simple treatment to prevent algae in the anolyte system for electrodeposition. Arie Porat Tzora Furniture, Israel [email protected] Some people have had luck with ultraviolet (UV) light. Some people filter more. One manufacturer recommends an "antiseptic" for their dye solutions. Heating kills most algae, as hot as the solution will tolerate shortens the time. You then have to filter the solution to get the dead stuff out or it messes up the finish on the parts. I have yet to figure out how the stuff can grow in some very noxious solutions. James Watts James Watts Inc. [email protected] How about plating in the dark? I would send some of the bugs to the local agricultural college to determine what you've got growing. Tom Pullizzi Team*Faraday Inc. [email protected] I don't have any experience with anolyte systems, but I just finished reviewing a bunch of earlier letters dealing with years of experience fighting algae/fungus/mold growth in plating rinses. Much of it may be inapplicable because of sensitivity of the anolyte, but it covers a lot of bases and may at least provide food for thought. Some of the proven approaches were: UV light (already mentioned); bleach (cheap, but will it destroy the anolyte?); peroxide and ozone generators (ditto); commercial algaecides for fish tanks, available from pet stores. To complete the list with some "out there" possibilities: potassium permanganate, formaldehyde, copper sulfate, silver nitrate, and potassium chromate. The more I go on, the better the UV is sounding to me. Ted Mooney Finishing Technology [email protected] 56
REMOVING POWDER COATING FROM MAGNESIUM How could one remove the powder coating from the surface of a magnesium wheel in order to polish the wheel? Also, would this be detrimental in any way to the performance of a racing wheel? John Hubbs College Station, Texas [email protected] For your purposes it sounds like the best course of action is to find some place that does plastic media blasting. They can remove the coating without damaging the magnesium and will do them one at a time. Also plastic media will not roughen the surface any further, important since you want to polish it later. Other chemical or mechanical means could either harm the piece or roughen the surface. Craig A. Burkart Texo Corp. [email protected] There are environmentally safe cleaning chemicals that have been found to be extremely aggressive for the removal of powder coatings. As a cold strip, a gel formulation may work well. Fred Wellman WSI Chemical Inc. [email protected] How would Mr. Hubbs decide whether chemically cleaning the wheels himself is more appropriate than finding a shop to do the plastic media blasting? If they were my wheels, I'd take them to a shop and let them make the decision whether to try mechanical or chemical means. Ted Mooney Finishing Technology [email protected]
.
POWDER COATING PRETREATMENT Is iron phosphating the best pretreatment for exterior articles? Are any laser devices or temperature gauging equipment available by which the temperature of any comer of an oven can be measured? Anil Tiwari Phoenix Fabricators, India [email protected]
© Copyright Elsevier Science Inc.
METAL FINISHING. OCTOBER 1998
What is the substrate? Aluminum? For aluminum, yellow chromate conversion coating is the best; however there are new nonchromate coatings claimed equivalent or better than yellow chromate. For steel substrates, I think you are right, iron phosphate is the best. There are several temperature "measuring and recording" instruments that travel with the workpiece in the oven so that you can see the temperature distribution versus time in the oven and of the workpiece itself. I think this is better than measuring the temperature of the oven's atmosphere. Timur Ulucak [email protected] For fear of oversimplifying pretreatment I won't list all the possibilities, but in order to determine what materials and methods of pretreatment to employ, you need to let everyone know the substrate, what conditions it will see, and what type of coating you intend to apply. Jim Cummings Buffalo Powder Coating [email protected]
AUTOPHORETIC COATING PROCESS Has anyone ever used, or does anyone know anything about, the autophoretic coating process? Anybody using it in the Northeast? Thomas Moffitt Mass. Office of Technical Assistance [email protected] Well, you have to remember that it is an organic coating, not a metallurgically bonded electroplating. So, if you want to replace paint, it may be a good fit. We looked at it for some heavy zinc-plated couplings and had to dismiss it because the parts are handled roughly, are used outside, and would chip and rust. Of course, that doesn't mean that all parts will chip and rust! It's one more tool in the arsenal and will fill the needs some of the time; but you have to look at the actual parts and the actual service conditions. Ted Mooney Finishing Technology [email protected]
~'C:,=;r=,c:amgs "I:i'i"':~~ii~{~~~~'I;:II,~I~bUilt)Instruments
· BEST PRICESi~::II~II~~fY
• Trade Ins Welcom.e))},,,,'\,
i41t-/ •.
• As£~~jt~~:~~gged, Easy To Use tiibaKrn Program for your old
. . ,.• '•.. •.•.•••••.. . . . .
Gl:lg~§c.mn~~.J?srg'~
Recalibration servi~;~':~::::~;;;'!jl!llii';. Ii ,,-,~swhile yours are se~1II11t :,t ,'I
;;ill ;
•
iii.::.. "lii¥,
by Justech Inc.
:::::::>-:',:::::>:':::.,:.:>:.:.:,.
JUSTECHIN@r{
GIlD
513-755-1280
cS'#IiIf-~FAtlIllktM~~~~/ Circle 027 on reader information card
METAL FINISHING • OCTOBER 1998
57
A well-known paint manufacturer (name supplied via E-mail) offers their paper "Comprehensive Comparison of Electrocoat vs. Autodeposition." Autodeposition and autophoretic are the same. Tyrone L. Caley Caley & Associates [email protected]
Hmm, does that supplier of electrocoating materials offer autophoretic coatings? If not, I'm not so sure that this work would have legitimate scholarly value. At the least I would want to see it challenged by a supplier of autophoretic coatings before I'd put full credence in its comprehensiveness. Ted Mooney Finishing Technology [email protected]
ADHESION OF LACQUER PAINTS TO SILVER· PLATED OBJECTS I am a fishing lure manufacturer. Getting lacquer paint to stick to silver-plated lures is my problem. Traditional methods are not durable enough. While I do not paint myself, my supplier has attempted to search through the automotive
industry and has come up with a fair product but not the standard I am looking for. Jim Martino Tamiron Sporting Goods Inc [email protected] Silver takes a chromate, not usually useful for silver plate, but usually good for paint adhesion. Is the paint over the entire lure, or only in selected areas? Tom Pullizzi Team*Faraday Inc. [email protected] Per the 1998 edition of the Metal Finishing Organic Finishing Guidebook and Directory, in an article by Earl C. Groshart, Consultant, new silver can be painted immediately following thorough cleaning, preferably vapor degreasing, or may be chromate conversion coated prior to painting. He notes that silver with sulfide tarnish, as long as it's not powdery, will take paint. Mike Moninger Thermospray, Sarasota, Fla. [email protected] We have had success applying lacquer-base paints to metallic surfaces (i.e., boat propellers to prevent algae
Singleton CCTn ChAMbER Introducing the New State ofthe Art
. •.•.•. •• ·~~p.geeaWO ••v..ilabl~···
Re::;~:ee •800428-3502 ..
e-Penonns Cyclic Corrosion Tests ·HowProfile Design for easy access .:.Power Assisted Cover
.:.Programmable Controller with Touch Screen Display .:.Available with full Humidity Control
mngleton
3280 W. 67th Place, Cleveland, 08 44102 216/651-7800 • 2161651-4247 Circle 050 on reader information card
58
Circle 070 on reader information card
METAL FINISHING. OCTOBER 1998
growth). We slightly sand the metallic surface, apply a base coat, followed by the paint application, then the protective coating. It has worked for us. Todd Miller Bronze Company II [email protected] PREPARATION OF STAINLESS STEEL FOR EPOXY POWDER COATING
I have a stainless steel enclosure and would like to epoxy powder coat it. What type of surface preparation is required for stainless steel in a powder coat finish application? Christopher Cioccio Union Switch and Signal [email protected] We have pretreated stainless steel with an alkaline cleaner, then either zinc phosphated or chrome phosphated, and painted with a TGIC. We used these chemicals and the painted parts passed the cross-hatch adhesion test. As always, getting the part clean is real important. Also, if the stainless steel mill finish is real smooth, a deoxidizer etch might help. Kelly Loch Carrier Transicol [email protected] Stainless steel does not lend itself to phosphating. I have seen instances where the stainless steel is zinc or cadmium plated and then phosphated. R.Sivakumar [email protected] I agree with the previous message, stainless steel does not accept a zinc phosphate coating. The important factor that you should be looking at is the surface roughness of the stainless steel. A roughened surface will accept paint more readily than a smooth one. In fact one of the ways to prepare stainless steel for painting is to sandblast or roughen the surface after cleaning. A wash primer may also be a way to get the final coat to adhere better. Craig A. Burkart Texo Corp. [email protected] FINISHING WROUGHT IRON FURNITURE
I have started a small company making steel furniture and other items (park benches, tables, etc.) I usually finish with a primer, then Rustoleum. Most of the items are made from hot-rolled steel, and some involve smithing. I've been descaling the steel using muriatic acid then rinsing with a hard stream of water. I can't seem to avoid getting some oxidation during the drying process. Here are my questions: How important is the descaling? How clean does the metal need to be? Am I going about it the right way? Is that little surface rust acceptable, or is there an easy way to eliminate it? (I can't always reach the parts with a wire brush, and that's unproductive). How does large-scale industry do it? How clean is their metal before powder coating, for examMETAL FINISHING • OCTOBER 1998
ple? Are there different kinds of primers? The stuff I'm making is looking good, I just need some guidance about how neurotic to be with the metal preparation. Thanks in advance for those of you willing to share your expertise. Art Thompson Art Works, Harrisonburg, Va. [email protected] Descaling hot-rolled steel is very important because the heat scale does not provide a very good adhesive surface for the coating. You are only missing one thing. A short-term corrosion inhibitor for the rinsewater. Once you have removed the scale, the surface of the steel is very active and will begin to corrode almost instantly because you have left the surface acidic. There are two ways to go here: You can phosphatize the surface with an iron phosphate solution with the pressure washer, or apply an alkaline rust preventive mixed with the rinsewater to prevent flash rusting while the parts dry. Both ways are being used by industrial plants that paint very large items from heavy equipment to dumpsters. Craig A. Burkart Texo Corp. [email protected] A cheap alternative to a phosphate system is to use a mixture of sulfuric and phosphoric acid to remove the scale. A thin layer of iron phosphate on the surface provides short-term protection. Laurence van Niekerk [email protected] I am manufacturing wrought iron furniture from hot-rolled steel (l if2-in. x 1;4.-in. bar stock for example). I have already powder coated some of our items but am not entirely happy with the "look." I would like some suggestions on what to use to finish these items and how to apply it. Greg Klein Loader Ltd., Ontario [email protected] How about a texture/splatter coat? This will hide some minor imperfections. Patrick Langan [email protected] See my question above for related information. I get a nice finish from Rustoleum Outdoor Satin, sprayed with an HVLP sprayer. It has a more natural, hand-painted look than the powder coat. Don't just use the standard black wrought iron look. Experiment with different colors, it will make your work stand out. I also have made some pieces where I polish the steel to a "pewter" look, than clear coat with lacquer. You can't hide any mistakes or slips of the grinder this way, though. Art Thompson Art Works, Harrisonburg, Va. [email protected] Ted Mooney is an independent consulting engineer based in MF Brick, N.J.
59