- Email: [email protected]
Red rust on zinc plated parts
One suggestion for pretreatment, which has helped US: after your final rinse, before plating, go back to the electroclean for 1 minute anodic, rinse, then plate. In some cases we do not use any acid pretreatment steps. Phil Juve, Electroless Nickel Plating, La., [email protected] If parts are heat treated for hardening it destroys the deposit’s ability to withstand salt spray testing and causes high phosphorus electroless nickel to act as 7 to 9% phosphorus. Twenty-five microns is a minimum requirement, 35 to 40 wil1 give better results. The famous 1,000 hours in salt spray is true only for simple sheets; parts with complicated shapes do not resist salt spray testing as well. Sara Michaeli, [email protected] What temperature is your electroless bath? The higher the temperature, the quicker the reaction initiates. (We have never been able to reproduce the manufacturer’s claims either). Patrick Crowley, Ingram & Glass Ltd., [email protected] RED RUST ON ZINC PLATED PARTS We are cyanide zinc plating a 3/4-in. diameter by 44-in. long 1010 steel tube, which has a hexagon inlay in one side.
We are getting severe red corrosion after the parts dry, only in the inside. We know that no protection is given (1/2-1 in. of coverage in the inside edges) in the inside, but our client wants to at least keep the parts without rust for 2 weeks while they are fully assembled. Our process cycle is as follows: soak clean; hot diluted sulfuric acid: rinse; anodic electrolytic degreasing; rinse; zinc plating; rinse; rinse; bright dip; blue chromate; rinse; hot rinse. We have tried skipping every single one of the steps mentioned, but the result is always the same. We have made the hot rinse alkaline but there was no improvement either. Rust inhibitors were also tested and the result was only a little bit better. Smal1 traces of “yellow chromates” are present in the inside of the hexagon edges and that is where the highest amount of red rust develops. Have any idea or clue on how to avoid or preserve the parts from red rust? Guillermo Luna, CENSA, Mexico, [email protected] Try dipping into an aqueous lacquer. Your last stage is acidic and this accelerates rusting. There are also proprietary products that prevent rusting for a short period. Sara Michaeli, [email protected]
COMETO NflPCOFOft BL1YOUR PlmlNG EQUIPMENTNEEDS TANKS POLYPRO STEEL ST. STEEL
?? ?? ??
AUTOMATIC PLATING SYSTEMS ?? HAND LINES ?? WASTE TREATMENT SYSTEMS
PLATING BARRELS REPLACEMENT PARTS PVC EXHAUST SYSTEMS
??
In addition we offer you a Service & Revamp Depattment to help you change, add to, or update your present Plating Equipment.
E
N
A
P
C
0
16 North Harwinton Avenue Terryville CT 06786 Telephone: 860-589-7800 ?? bax: 860~&9-7304
<
Circle 050 on reader information card
METAL FINISHING
??
OCTOBER
1996
57
1 don’t quite understand the “hexagon inlay” description, but 1 can at least picture tubes. Blue chromates have an insufficient amount of hexavalent chromium to provide any real corrosion resistance to bare steel, and since you probably can’t switch to yellow chromate for cosmetic reasons, 1 would agree with Sara that a water-based lacquer is probably your best bet. You can obtain this from a local supplier, or discuss it with a lacquer manufacturer. But 1 also think that drying the parts is critical to avoid early rusting. A hot forced-air dryer is probably indicated. Ted Mooney, Finishing Technology, N.J., [email protected]
ADHESION ON LEAD BULLETS We have recently started copper plating lead tast bullets up to 100 micrometers in a cyanide copper bath. We are having a problem with the adhesion of the copper on the lead. The process that we are using is as follows: hot soak at 60°C; electroclean at 60°C; rinse; rinse; pickle in fluoride based acid; rinse; rinse; plate in cyanide copper at 60°C; rinse; rinse; passivate in chromic acid. 1 would appreciate any comments or advice. Martin Swart, Martin Lead Bullets, [email protected]
Just a wild guess to get things started, but have you checked to make sure you are not dragging hexavalent chromium up and down the line in cracked rack coatings or improperly rinsed barrels, or routing chrome rinsewater into the preplate rinses? 1 am assuming that your supplier set you up with the preplate cycle. It looks okay except: Are you using a copper strike? A hot, full strength copper cyanide may not give you perfect adhesion without a strike. Torn Pullizzi, Team*Faraday, N.J., [email protected] It seems to me you are going from an acid almost directly into a cyanide solution. This wil1 cause problems. We immersion clean, rinse, rinse, weak fluoboric acid rinse, rinse, rinse, weak sodium cyanide rinse, rinse then into the copper. We don? passivate. We don? strike in our barrel operation, and 1 assume you are barrel plating. David Guleserian, [email protected]
Ted Mooney is an independent consulting engineer based in N.J. MF
Kinnelon,
Chambersof Choice Atotech offers a complete selection of rugged test chambers that meet over 40 major ASTM, automotive, military and commercial specifications:
Salt Fog ??Cyclic Corrosion ??Salt Solution Spray
Wet/Dry Cyclic ?? Humidity ??CASS & Acetic Acid ??
Equipment also available to do SO, testing, immersion tests, fungus, rain and soapy spray.
Put US to thetest. For more details on our complete line of test chambers, cal1 or write:
atotech 20026 Progress Drive Strongsville, OH 44136 Phone: 216-572-7800 ?? 1-800-433-8336 Fax: 216-572-7820 http://www.atotechusa.com Circle 076 on reader information card
58
METAL FINISHING
9 OCTOBER
1996
We are getting severe red corrosion after the parts dry, only in the inside. We know that no protection is given (1/2-1 in. of coverage in the inside edges) in the inside, but our client wants to at least keep the parts without rust for 2 weeks while they are fully assembled. Our process cycle is as follows: soak clean; hot diluted sulfuric acid: rinse; anodic electrolytic degreasing; rinse; zinc plating; rinse; rinse; bright dip; blue chromate; rinse; hot rinse. We have tried skipping every single one of the steps mentioned, but the result is always the same. We have made the hot rinse alkaline but there was no improvement either. Rust inhibitors were also tested and the result was only a little bit better. Smal1 traces of “yellow chromates” are present in the inside of the hexagon edges and that is where the highest amount of red rust develops. Have any idea or clue on how to avoid or preserve the parts from red rust? Guillermo Luna, CENSA, Mexico, [email protected] Try dipping into an aqueous lacquer. Your last stage is acidic and this accelerates rusting. There are also proprietary products that prevent rusting for a short period. Sara Michaeli, [email protected]
COMETO NflPCOFOft BL1YOUR PlmlNG EQUIPMENTNEEDS TANKS POLYPRO STEEL ST. STEEL
?? ?? ??
AUTOMATIC PLATING SYSTEMS ?? HAND LINES ?? WASTE TREATMENT SYSTEMS
PLATING BARRELS REPLACEMENT PARTS PVC EXHAUST SYSTEMS
??
In addition we offer you a Service & Revamp Depattment to help you change, add to, or update your present Plating Equipment.
E
N
A
P
C
0
16 North Harwinton Avenue Terryville CT 06786 Telephone: 860-589-7800 ?? bax: 860~&9-7304
<
Circle 050 on reader information card
METAL FINISHING
??
OCTOBER
1996
57
1 don’t quite understand the “hexagon inlay” description, but 1 can at least picture tubes. Blue chromates have an insufficient amount of hexavalent chromium to provide any real corrosion resistance to bare steel, and since you probably can’t switch to yellow chromate for cosmetic reasons, 1 would agree with Sara that a water-based lacquer is probably your best bet. You can obtain this from a local supplier, or discuss it with a lacquer manufacturer. But 1 also think that drying the parts is critical to avoid early rusting. A hot forced-air dryer is probably indicated. Ted Mooney, Finishing Technology, N.J., [email protected]
ADHESION ON LEAD BULLETS We have recently started copper plating lead tast bullets up to 100 micrometers in a cyanide copper bath. We are having a problem with the adhesion of the copper on the lead. The process that we are using is as follows: hot soak at 60°C; electroclean at 60°C; rinse; rinse; pickle in fluoride based acid; rinse; rinse; plate in cyanide copper at 60°C; rinse; rinse; passivate in chromic acid. 1 would appreciate any comments or advice. Martin Swart, Martin Lead Bullets, [email protected]
Just a wild guess to get things started, but have you checked to make sure you are not dragging hexavalent chromium up and down the line in cracked rack coatings or improperly rinsed barrels, or routing chrome rinsewater into the preplate rinses? 1 am assuming that your supplier set you up with the preplate cycle. It looks okay except: Are you using a copper strike? A hot, full strength copper cyanide may not give you perfect adhesion without a strike. Torn Pullizzi, Team*Faraday, N.J., [email protected] It seems to me you are going from an acid almost directly into a cyanide solution. This wil1 cause problems. We immersion clean, rinse, rinse, weak fluoboric acid rinse, rinse, rinse, weak sodium cyanide rinse, rinse then into the copper. We don? passivate. We don? strike in our barrel operation, and 1 assume you are barrel plating. David Guleserian, [email protected]
Ted Mooney is an independent consulting engineer based in N.J. MF
Kinnelon,
Chambersof Choice Atotech offers a complete selection of rugged test chambers that meet over 40 major ASTM, automotive, military and commercial specifications:
Salt Fog ??Cyclic Corrosion ??Salt Solution Spray
Wet/Dry Cyclic ?? Humidity ??CASS & Acetic Acid ??
Equipment also available to do SO, testing, immersion tests, fungus, rain and soapy spray.
Put US to thetest. For more details on our complete line of test chambers, cal1 or write:
atotech 20026 Progress Drive Strongsville, OH 44136 Phone: 216-572-7800 ?? 1-800-433-8336 Fax: 216-572-7820 http://www.atotechusa.com Circle 076 on reader information card
58
METAL FINISHING
9 OCTOBER
1996