Blackening steel parts

Probably a repeat question (sorry) but would appreciate suggestions for obtaining a good durable finish in blackening steel parts. I guess I would prefer a cold method but would consider other methods.

Thanks

Ron

Seem to remember there was a thread about this subject not too long ago. Hang in there,someone will be along soon.

Chronos do a blackening kit, but not cheap, GLR also do but again not cheap...

One or more of the following may give some thoughts to start with and/or develop the discussion:

Help with cold steel blackening

Blackening mild steel

Blackening steel - Caswell Black-Ox kit

Am I blackening steel correctly?

Chemical blackening

Regards,

Phil

Edited By Weary on 28/11/2018 16:48:18

I use the Black-it kit. Got mine from Blackgates but seems to be available from several sources.

I'm happy with the results.

Rod

Same as Roderick, Blackgates or EKP supplies sell them,smallest kit under twenty quid. My kit still going strong after 5 years of regular use.

Weary’s links are all from searching with the word blackening. Blacking, in the search box, may give you even more to go at.

Much would depend on how you define "good" and "durable" for a finish - and how big the parts are.

As the link above to "Blackening mild steel" shows, many have found supermarket sunflower or rapeseed oil to be effective.
Heating to red and dropping in sunflower oil produces a nice black finish on steel every time for me. The oil protects the surface but. If you don't like the residue, clean off and apply black shoe polish to prevent rusting.

A cold method which is cheap and easy but very dependent on an excellent surface to begin with is "gun blue". (I've had variable results if the surface was not completely degreased first). It's quick to apply (wear disposable gloves) and wash off after. Do though coat with the aforementioned shoe polish or rusting occurs quickly. Put 'gun blue Bisley' into Google & you'll find YouTube vids on doing it and sellers. A small bottle from Bisley shop has lasted me for years.

There has recently been an interesting posting on the HSM forum for blackening steel using ammonium nitrate. This seems to avoid most of the complications and dangers associated with normal hot blackening baths. see:

http://bbs.homeshopmachinist.net/threads/77586-Black-oxide-experiment

When I have obtained the material I intend to give this process a try.

Mike

I've never used this particular kit myself, but Frost's have been selling it, or similar for years.
I doubt they's continue if they got regular complaints; occasionally it's sometimes better to go to a reputable third party supplier for just that reason.

N.B. Don't be fooled by the initial £14.99 price that comes up.

Bill

Edited By peak4 on 28/11/2018 20:14:32

Like I said,someone would be along soon !!!

We used to dunk our hot bits of steel in old engine oil to blacken it, is this now forbidden?

Phil.

Has anyone noticed the acronym of Frost Auto Restoration Techniques Ltd. ?

And yes that is their registered company name...

Neil

No, but used engine oil is rich in nasties, I use rapeseed oil which works just as well and costs almost as little.

Neil

I agree that rapeseed oil should be a lot nicer than engine oil, but I wonder why people pay for blackening kits for mild steel?

Used cooking oil from the local chippy should be good as well.

Phil.

Nearly as bad as the surname of the President of the USA, who for the benefit of non UK readers is a euphemism for flatulence. Seems appropriate somehow.

"Nearly as bad as the surname of the President of the USA, who for the benefit of non UK readers is a euphemism for flatulence. Seems appropriate somehow"
I mistyped his name recently and the spell checker came up with President Turnip, decided to leave it in as quite appropriate.

Not too sure I'd be trying ammonium nitrate, apart from being a reasonable fertiliser its a reasonable explosive.

Sound, published evidence that well-used, old engine oil is full of carcinogens.

My favorite acronym was Suzuki's little 250cc commuter bike a few years ago: the Across New Urban Sports.

In a bike world full of FZR's, CBR's, VFR's, it was only ever going to be known as one thing.

I use the hot bath method. It runs at 135 to 140 C. So some care is needed. It works very well and I have never had any issues with it all. The downside is the time required to heat the bath, and the cleanliness of the parts. Some steels with high chrome content do not blacken very well with this process.

It is cheap to set up though and the basic formula is very simple. My current bath starts with 10 deionised water chlorine free. Chlorine free is important. 10 L of caustic soda pearl, or alternately 10 L of concentrated caustic soda solution, Mix water and pearl very slowly adding the pearl. Ready made solution does not need any extra pearl add. Then after it is close to room temp add 10 l of sodium Nitrite powder/crystals. Mix etc, use care as this is very caustic. Slowly heat to 135C or untill it just simmers. Stir often. The parts will take about 5mins for small sections (less than 25mm thick) to 15mins for 50mm sections) . Remove from the bath, let hang and drip off, then wash in hot water and I use vinegar water to neautralise the basic solution. Dry and oil. All done. This is really a more commercial set up, but does work very well. There are slight adjustments to the basic formula, like adding sodium Nitrate, and some add other stuff as well. If you have a set up in such a manner that you may drop and splash parts into the hot bath, then your set up is wrong. It needs to be arranged so that you can not make any splash of any kind , no matter the reason. You do not get a second chance with hot caustic things. But I am happy with with I have, have been since 09 when I started doing this commercially. Do not allow any non steel parts to contact the bath either.

Neil