Thread: Chinese Black Nuts, Bolts & Washers

Originally Posted by Jim Ferrous

How do they get the black finish on Nuts, Bolts & Washers that come with most of the machinery that comes out of China?

I'd like to be able to duplicate the finish.

I think it is oil blackening but I am probably wrong. I know RayG & Josh (Brombodigan???) were doing it to some parts for one of the machines they were restoring some maybe shoot them a PM. They are always very helpful in my experience.

It's a phosphate coating, also known as parkerising. DIY instructions at the link

https://www.woodworkforums.com/f65/pa...uctions-42220/

They may also be black passivated zinc plated. This the better corrosion protection compared to the 'blue' (silver coloured) or 'yellow' (gold coloured) passivated zinc plated surfaces on new bolts. You should be able to tell by polishing the black surface and it should come up shiney silver zinc colour eaisly and quickly, compared to steel colour silver with more effort if it was parkerised.... If it was just an oil blackening or paint, acetone may wipe it off.... But I'm no expert and find it difficult to tell the difference.

Jim,

I had a crack at the recipe linked by Splinter and originally posted by Grahame Collins. https://www.woodworkforums.com/f65/pa...4/#post1208286 A bit of the way into the thread Ian "Tinkera" posted some photos of a collection of neat toolholders that he had blackened using a product called Blackfast. I bought some of the stuff and posted some photos of the results I achieved using it. Less messy than the stove top boil up. https://www.woodworkforums.com/f65/bl...9/#post1217328

My favourite form of blackening ( in reality blue purpleing ) is with a Mapp torch and oil.

BobL has used a fuming process utilising nitric and hydrochloric acid https://www.woodworkforums.com/f65/my...3/#post1522350 Great results but a fair bit of time involved.

Bob.

Thank you all for the replies, much appreciate them.

I'll throw a couple more out there
1. Copper/Selenium Blackening
2. Caustic Black Oxiding (I'm guessing this would be the China method for bolts?)
3. Black Dyed Oxalate Coating

-Josh

Oh, oh, hang on, that was "Chinese" process in the op's request...

(sound of typing into google for 'steel blackening' +cheap, -safe, -health, -ohs, -ecological, -nontoxic -workersafety )

And you get a process using water, caustic soda, and a nitrate (potassium nitrate, amonium nitrate, sodium nitrate). Mix and bring to boil, suspend metal in the solution for 15 odd minutes. Mind you dont get the caustic splashed on you!

Originally Posted by Brobdingnagian

I'll throw a couple more out there
1. Copper/Selenium Blackening
2. Caustic Black Oxiding (I'm guessing this would be the China method for bolts?)
3. Black Dyed Oxalate Coating

-Josh

Josh, were you discussing the process that Rod was using in Wagga with him, or was that Ray? I just remember a board with 10 or so 4" poly pipe "tanks" standing up on it, numbered 1-10 (or however many) and a description of what was in each. I was probably too busy controlling Arthur to pay enough attention......

Ew

There is a article on this topic in the next edition of MEW magazine..... Mike

Originally Posted by Ueee

Josh, were you discussing the process that Rod was using in Wagga with him, or was that Ray? I just remember a board with 10 or so 4" poly pipe "tanks" standing up on it, numbered 1-10 (or however many) and a description of what was in each. I was probably too busy controlling Arthur to pay enough attention......

Ew

Oh Yeah, it was a cold process, I can't remember the name of the company that made the products, but most of the 10 tubes were for rinses from memory.
-J

This is excellent question, I happen to have some rusty chrome plated wheel nuts to attack.