Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Zinc plated thread rods: Q&As re. plating, corrosion resistance of chromates
Q. I am somewhat familiar with the zinc dichromate coating process, but I am not sure which color of dichromate is best for my application. I currently use both blue and yellow dichromates in different applications. I am considering using zinc dichromate on a part in a more corrosive environment than my current parts are subjected to. I was wondering if there is any difference in corrosion resistance between the blue, yellow or other colored dichromates.
Nick Bohr- Aurora, Illinois, USA
2002
A. Olive drab is more corrosion resistant than yellow, which in turn is more corrosion resistant than blue or clear. This is because the darker colors have (or have more) hexavalent chromium in them. Figure 150 hours to white rust with olive drab chromate, 96 for yellow or black, 12-24 for clear. However, be wary that the age of hexavalent chromate conversion coatings is drawing to a close for environmental reasons, and the color of the trivalent chromates of the future is usually just a matter of dye.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002
RFQ: I need a quote for Black Zinc plating. 300 pieces. 3/8-16 x 10' threaded rod 1008 pieces. 1/2-13 x 10' threaded rod Plate in accordance with ASTM B633 Type II Black SC 1. Need response ASAP.
Thank you,
George K [last name deleted for privacy by Editor]plating shop - Sun Valley, California, USA
2003
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Q. I'M DOING A SCIENCE FAIR PROJECT THAT STATES "DOES SALT WATER AFFECT THE RATE OF RUSTING". MY PROBLEM IS THAT I'M USING ZINC PLATED THREADED RODS.I DON'T KNOW IF ZINC IS A METAL THAT PRODUCES RUST. HOW WILL MY EXPERIMENT COME OUT IF MY METALS DON'T RUST. I LOOKED EVERYWHERE FOR MY ANSWER BUT NO SITE HAD IT. NOW I'M PUTTING IT IN THE HANDS OF VERY SMART PEOPLE.
THANKS TO ANYONE WHO DID OR AT LEAST TRIED TO HELP ME :)!
student - Zachary, Louisiana, USA
2007
2007
A. Hi Kaylon. The threaded rod is made of steel with a thin coating of zinc electroplated onto it. The zinc makes the rod shinier, but the real reason it's there is to protect the steel from rusting. Zinc does corrode although it doesn't rust, but it will make the rusting of the steel take longer and it complicates your project.
If it's not too late, go to a hardware store and get "masonry nails". Make sure they're not shiny. These are made of a hard steel. They usually aren't coated at all, I think, but because of their flat shape you should be able to easily sand off any coating. Then you'll have a bare steel surface and no zinc to complicate things.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
RFQ: We are looking for a company that can plate ASTM B633 Type II zinc yellow RoHS compliant on threaded rod in
ASTM A193 B7 ,up to and including 12 ft in length. Volume would be
40,000 to 50,000 lbs per shipment; 4 or 5 shipments in a year.
Fastener Distributor - Apopka, Florida
July 7, 2008
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Threaded steel rod, zinc plated with trivalent chromate screwed into aluminum plate
Q. We are considering an aluminum mounting plate to be used with our steel threaded rods. the rods are zinc plated with a trivalent chromate outer coating. I am concerned about the reaction between the aluminum and the steel. Is there an ideal coating for the aluminum in this application?
Ed ReszenskiProduct designer - Weymouth, Massachusetts
November 3, 2008
November 3, 2008
A. Hi, Ed. This is perhaps not "ideal" depending on environmental exposure, because aluminum and zinc are not galvanically compatible, but they're not too far away. If the aluminum mounting plate has threaded holes, the plate too should be chromate conversion coated. If the plate has through-holes, and zinc plated nuts are used on the rod, the plate could be anodized, which would afford greater corrosion protection and less galvanic corrosion issues. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi to all ...
What is the difference between zinc plated threaded rod and BICHROMATED zinc plated threaded rod? Which one is better and what is the advantages and disadvantages for both.
Thanks.
- saudi Arabia
February 23, 2015
A. Hi Moutaz. Virtually all zinc plating receives a chromate conversion coating after it to deter white rust.
Still, to decide if there is a difference between two finishes, you would need to know the actual specifications, not just the slang which is used internally or in sales pap. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 2015
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