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Metal finishing Q&As since 1989
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Unpassivated galvanized steel
Q. I have specified the following for metal covers used in our product:
MATERIAL: STEEL SHEET ZINC-COATED (UNPASSIVATED GALVANIZED) AS PER ASTM A653/A653M-01, CS STEEL (TYPE A OR B), COATING DESIGNATION Z275, MINIMIZED SPANGLE (MAX. SPANGLE 1/8 INCH) NOT CHEMICALLY TREATED.
0.94 mm THICK (20 GAUGE).
The need for 'unpassivated galvanized steel' comes from a requirement to be compliant to the EU RoHS directive.
I contacted a steel producer and they informed me that 'unpassivated galvanized steel' is the only compliant galvanized steel.
1. What is 'unpassivated galvanized steel'?
2. How do I ensure I get 'unpassivated galvanized steel'?
3. Can 'unpassivated galvanized steel' be bent(~30 deg) and still provide rust protection?
4. The 'unpassivated galvanized steel' has to be electrically conductive; does it have to be cleaned to ensure a good conductive surface?
Regards,
- Ottawa, Ont. Canada
2006
A. Dear Sir
1-Galvanized steel-zinc coated-passivation mean to lower the activity, Most of the time passivation will change the colour ,other than the zinc, metallic colour.
3-Zinc is ductile, I believe yes you can bend, if in doubt check after bending with a magnifier for cracks.
4- Yes it is conductive.
Good luck
![Cair Shishani](../portraits/khair_shishani.jpg)
Khair Shishani
aircraft maintenance - Al Ain, UAE
2006
Q. Mr. Khair Shishani: Thank you for your response.
The EU has granted an exemption pertaining to HexChrome (VI) for one year, but China has no exemptions.
The unpassivated galvanized sheet steel; non-oiled, will probably exhibit 'white rust' after a period of time, which would affect the surface conductivity that I need.
The questions is, how long would it take for the 'white rust' to appear in a climate controlled environment; telco central offices?
regards,
- Ottawa, Ont. Canada
2006
A. Joe,
I happened to be in attendance just yesterday during a panel discussion at a technical conference session on chrome substitutes at Sur/Fin 2006 where the question came up of what to do about galvanized parts that require RoHS-compatible passivation. At least one of the suppliers of the new TCP treatments designed for aluminum (who include SurTec, Luster-On, Metalast and Henkel) reported successful experience in applying this coating to galvanized parts. Please follow up with them and you may find that the answer already exists. Good luck.
![Ted Mooney, finishing.com](../portraits/ted_mooney_beach.jpg)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006
A. I don't know if this would help; but I have left a piece of mild steel coated with zinc from a alkaline bath for two years in a drawer in the office and there was no noticeable sign of corrosion. Good luck
![Cair Shishani](../portraits/khair_shishani.jpg)
Khair Shishani
aircraft maintenance - Al Ain, UAE
2006
A. Might want to try selecting a CRS with trivalent chromium in the passivate instead of hexavalent chromium. Trivalent chromium is RoHS compliant.
Abu Dhabi- Linthicum, Maryland, USA
2006
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