plating, anodizing, & finishing Q&As since 1989
Mechanical galvanizing on HDG fasteners
October 9, 2012
Q. One of our US customers asked for mechanical galvanized quoting on HDG finishing fasteners and the quantity of LEAD should not exceed 100 ppm.
But this requirement cannot be achieved by most of the factories. Is it so difficult to achieve this requirement.
Can you suggest some factories who can meet this requirement.
- Guang Zhou, China
A. Hi Ghulam.
Your inquiry is a bit confusing to me because people do not (to my knowledge) apply mechanical galvanizing on top of HDG (hot dip galvanized) fasteners. Are you asking for mechanical galvanizing instead of hot dip galvanizing on the fasteners? Remember that you must figure out how thick you want the coating to be, whether that is a reasonable and practical thickness for the given technology, and what (if any) effect it will have on the threading dimensions.
This site is made possible by supporting advertisers for camaraderie and technical discussions, and we can't spend their money steering potential customers to their competitors, so we don't print commercial sourcing info (it also leads to spam and hostility). But Plating Systems and Technologies [a finishing.com supporting advertiser] is a world leader in mechanical galvanizing systems and may be able to help you locate a source. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Ted is right; mechanical galvanizing is used as an alternative to hot dip galvanizing, not as a supplement. I've been involved with mechanical plating and mechanical galvanizing for over 30 years and have never seen mechanical galvanizing over hot-dip, even though it is technically possible. Hot dip galvanizing is often performed using Prime Western Zinc, which has 1.4% lead. That's 14,000 ppm. In North America, mechanical galvanizing is performed using zinc dust that is produced by distillation from Special High Grade Zinc (ASTM B6-12
[affil. link]). This grade has 0.003% maximum lead (30 ppm) and the distillation process (the Larvik Process) further reduces the lead level. Zinc dust for mechanical plating and mechanical galvanizing should meet ASTM D520
[affil. link], Type III, which has a maximum lead content of 0.002% or 20 ppm.
Since the customer is in the USA, if you ship the fasteners to the USA black, all of the North American mechanical galvanizers could coat these fasteners and easily meet the lead requirements.
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.