Summary for mid temp black oxide Discussion
mid temp black oxide on wood screws is the thread’s focus, but the discussion is really about how Chinese suppliers may be delivering black oxide screws that look dry and still resist corrosion. Vivek Sharma notes that the finish seems thinner than CED and that an HCl dip exposed bare metal immediately, which helped rule out other coatings like paint or black zinc. Kishan Patel says he is trying to match the Chinese result for drywall screws and that his black oxide plant costs are higher than expected at 50–70 tons per month. Ted Mooney, P.E. replies cautiously that he has no idea what the Chinese competitor is doing, but suggests trying to bake screws after hot black oxiding to dry the oil onto them. He warns that black oxide without oil can flash rust in about 15 minutes, so any dry-looking finish likely depends on some form of post-treatment or hidden protection.
adv.
Q. My name is Vivek and I have a question for all the experts: how to produce black oxide at mid temp conditions without any rub off or smut on wood screws? Also it is free from oil as I got some samples from China where they are manufacturing screw and coating it with black oxide in such a manner that there is no oily touch or smell on the pieces and it is black free from any rub off or smut.
Vivek sharma
– Mumbai and Maharashtra, India
December 8, 2022
? Hi Vivek. How do you know it was a mid-temperature process, or that it’s even black oxide as opposed to black zinc or e-coating or QPQ nitriding?
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
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Q. Sir,
Thanks for your reply.
I speculated it to be black oxide as the coating thickness is below 5 micron whereas in CED
⇦ huh? coating the thickness range from 10 to 20 micron
Also when I dipped the component in HCl acid it immediately turned into bare metal pcs; there was no reaction observed.
Within seconds I was able to see the bare metal
In case of CED generally we can observe paint flakes stripped off from the surface.
Also in case of black zinc because of zinc it shows some reaction which was not seen either.
Vivek sharma [returning]
Employee – Mumbai
December 15, 2022
Q. I am also looking for that. Like how is China supplies black oxide finished dry wall screws without oil. And they have a nice corrosion resistance.
Please guide me through.
As i have installed a black oxide plant but for screws my cost is going much higher than thought.
I have quantity of 50-70 tons per month for black oxide.
Kishan Patel
Electroplating company owner – Ahmedabad, Gujarat.
A. Hi. I have no idea what your Chinese competitor is doing, but have you tried baking the screws after hot black oxiding in order to try to dry the oil onto them? Black oxide with no oil can flash rust in 15 minutes.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.