Author Topic: Parkerising technique  (Read 7889 times)

Offline Buksie

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Parkerising technique
« on: September 03, 2013, 01:22:20 AM »
Hi Guys

As promised in the introduction section, here is my write-up for my parkerising formula.

I recently decided to try my hand at Parkerising as it would be a very use full technique to coat some of my home made tools and many other things I make in my workshop. I did a little research and some experimenting and found that the following works for me.
To make up a Parkerising liquid you will need manganese dioxide 6 heaped tablespoons, about 500ml of phosphoric acid (rust remover) and 2L clean boiled tap water (cooled down) and a small piece of steel wool.
You can buy manganese dioxide or go the cheap route and source enough from old torch batteries.
To get the manganese dioxide out of the battery you have to carefully cut the zinc casing open which forms the cathode of the battery, you only need the black crumbly stuff, avoid contact with the silver paste in the centre, it will give you a nasty burn as it is corrosive.
Mixing the ingredients in a large plastic bottle makes it a little safer as it will prevent the chemicals splashing all over the place.
Put the water in the bottle and add the manganese dioxide, add the acid last, you will see that the manganese dioxide does not dissolve in the liquid, it sinks to the bottom.
Before you start the Parkerising process the part you want to coat must be degreased and any rust removed. I sandblast them and just wipe the part off with a clean rag and some acetone.
Now you are ready to start the Parkerising process, pour the mixture in a stainless steel pot or pan of suitable size, obviously an old one that is not going to be used for cooking again, put a small piece of steel wool (about the size of a marble) in the mixture and bring it to boiling point. When it starts to boil put the part in the pot and make sure it is covered by the liquid, I prefer to turn it over about every 5 minutes. Normally 20 minutes is enough to give a nice even coating, obviously bigger parts will take longer. I allow the mixture to boil, this will cause some frothing of the liquid but it works for me as I already mentioned.
I must be honest in saying that my description of this process sound far more accurate than it really is or needs to be, I found that the mixture still worked well after adding just water to compensate for evaporation, it only takes a little longer to get a nice dark coating but the end product is still the same.
In the photos you can see that I sandblasted my mauser rifle parts before coating them, they came out really nice and then my tangential tool holders that was also coated.

I hope this is helpfull information, any feedback, comments or advice will be welcome, there is always room for improvement on my side.

I hope everything is clear enough, if not, just ask.

B.

« Last Edit: September 05, 2013, 12:18:25 AM by dsquire »

Offline awemawson

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Re: Parkerising technique
« Reply #1 on: September 03, 2013, 02:45:22 AM »
Thanks for that Buksie - as I said earlier I'd bought the phosphoric acid and manganese dioxide some months ago but not got round to trying it out. Time for a few experiments !
Andrew Mawson
East Sussex

Offline modeng200023

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Re: Parkerising technique
« Reply #2 on: September 03, 2013, 03:06:59 AM »
Thanks from me too. I didn't know it was that simple.

John

Offline Pete W.

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Re: Parkerising technique
« Reply #3 on: September 03, 2013, 03:55:14 AM »
Hi there, Buksie,

That's very interesting and potentially useful to me, thanks.

Have you done any measurements to see if the parts grow after the treatment?

(Your pictures were too big for my screen when expanded.  I recommend the use of Faststone photo resizer - see the 'Gallery' section of this site.  It's free to download.)
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline Meldonmech

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Re: Parkerising technique
« Reply #4 on: September 03, 2013, 04:28:59 AM »
Hi
       Must try this, already have all the ingredients, just need to find the time.

                                             Cheers  David

Offline awemawson

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Re: Parkerising technique
« Reply #5 on: September 03, 2013, 04:47:24 AM »
I can see the need for a 'Parkerising VAT' in the workshop. I would dearly like to Pakerise the fingers of the Edwards Box Pan Folder that I am currently re-building, but each one weighs about 15 kgs and there are 12 of them I think.

I visualise something like a tea urn with a built in thermostatically controlled heat source, suitable suspension points, and a lid to keep the vapours in. I see you mention using a stainless steel pan - maybe there is a stainless catering urn I could press into service. (It just so happens the postman has just delivered a catalogue from a catering supplier I've used in the past!)

Andrew Mawson
East Sussex

Offline PekkaNF

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Re: Parkerising technique
« Reply #6 on: September 03, 2013, 05:25:31 AM »
Very nice write-up. Did you encounter any problems and how they were encountered?

I have experimented pretty much same way. I did read a lot and got really confused. There was really many different receipts with very many different ingredients and some claimed very different results from "same" methods.

I pretty much did the same than you with few differences:

I managed to source clean 85% phosphoric acid, therefore it was easier to calculate "exact" concentration, which actually does not seem to be very important, but it is nice to know for future use.

I also managed to source very nice manganese dioxide from a pottery supply store, turns out it is used for coloring pottery or something.

I used a cheap deep-frier, it had all the works I needed. Vat, thermostat, immersion heater. I used it as baine marie to bring it to a rolling boil and one vat of parkerizing solution was brough to 92C something....IR thermometer was not very reliable on these, but I found very cheap and good enough caramel thermometer from cookingware shop.

Looks like avoiding grease/dirt is the most fundamental thing....I even found very cheap clean uncoated/lubricated iron wire - it was sold to tie rebars together. Bundle of 0,7 mm 30 cm long precut wire cost few euros.

Tried liquid lawn fertilizer in different composition as preblack and it seemed to produce a bit more even results.

I have had hard time figuring out proper post rinse, water repellent (de-water) and oiling. Everything seem to work. Everything seems to be used. Worst idea was to use alcohol....needed instant oiling or developed some kind of rust right under your eyes.

I got best results with boiling hot distilled water rinse, followed by compressed air and then immersed into warm straight mineral oil and then let oil drip out until next day.

Pekka

Offline Buksie

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Re: Parkerising technique
« Reply #7 on: September 03, 2013, 09:07:26 AM »
Hi Guys

Yes I agree this is a usefull process, it makes my parts look a little better. One thing I forgot to mention, I found that if a part is case hardened it appears to be lighter in colour compared to the same part that was not hardened, anyone here with the same observation?

PeteW: I have not parkerized precision parts with close tolerances where measuring was required, I did however read on one of the many internet sources that Parkerising helps with oil retention and improves the wear life and bedding of the part, I have not put this to test yet, this will definately be a future experiment and something to try.
PekkaNF: You confirmed my observation that the recipe does not have to be followed by the letter, you mentioned that you use lawn fertiliser as a pre black, would you mind giving some more information on that process? Is it KNO3 based fertiliser?
awemawson: to me it sounds more like you want to construct a industrial setup, I think it is a good idea to use a thermostatically controlled vat to control the temperature, I am convinced you will get more consistent results if you can regulate the temperature of the mixture, that way you can time the process and get the same shade of black for diffirent parts, I think.

BR.
B.

Offline awemawson

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Re: Parkerising technique
« Reply #8 on: September 03, 2013, 09:19:40 AM »
awemawson: to me it sounds more like you want to construct a industrial setup,  I think it is a good idea to use a thermostatically controlled vat to control the temperature, I am convinced you will get more consistent results if you can regulate the temperature of the mixture, that way you can time the process and get the same shade of black for different parts, I think.

BR.
B.

 :ddb: :ddb: Well if you're going to do it you may as well set yourself up properly  :ddb: :ddb:
Andrew Mawson
East Sussex

Offline PekkaNF

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Re: Parkerising technique
« Reply #9 on: September 03, 2013, 01:25:25 PM »
.......
PekkaNF: You confirmed my observation that the recipe does not have to be followed by the letter, you mentioned that you use lawn fertiliser as a pre black, would you mind giving some more information on that process? Is it KNO3 based fertiliser?

I etched the part 10 mins of "preblack solution" that consist raw liquid fertilizer and 3% of phosphoric acid at room temperature (about 20C). Then hot water rinse of 10 minutes before dunking into park solution.

The fertilizer was NPK 13-1-3
Sorry the choice of languages
http://www.nelsongarden.fi/prod/Giva-Grass-GTI-25l_374331/Kasviravinteet-Giva_47979/FIN/SEK#

Burlap tells that the Nitrate is 4%, ammonium nitrate 3% and urea 6% plus 1% P and 3% K. This was pretty much the only form of nitrates I could get.

I made some notes of using also 3% HCL 11 min. It did react, but had no apparent effect on end result with tempering steel.

If anybody is interested my recipie for park is:
19,5g phosphoric acid ( 23g of 85% phosphoric acid)
1 litre Purified water
10g manganese dioxide, most of it does not dissolve
4 g of degreased wirewool

Cured classical way. Funny thing was that first 90C park did not produce very black, but next 92C experiment produced flocking mentioned often and made very nice jet black parts.

I am a bit middle of interior decoration of my garage (got grinding machine into garage just two hours ago...still on dollies) and some sundry things to make before I'll make some more tools that needs emergency bling.

Pictures:
Park with deep frier
Several end products, the one on the top with fertilizer pre-black
The preblack solutio with example, as you see I used sanding not sand blasting (I don't have sand blasting equipment).


Pekka


Offline Pete W.

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Re: Parkerising technique
« Reply #10 on: September 28, 2013, 10:45:21 AM »
Hi there, all,   :wave:   :wave:   :wave: 

Nobody has answered the question in my earlier post - does this process cause the component to 'grow'?  :scratch:   :scratch:   :scratch: 

For example, if the part has a screw thread, do you have to mask it to preserve the fit?
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline Sid_Vicious

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Re: Parkerising technique
« Reply #11 on: September 28, 2013, 01:03:45 PM »
Since parkerizing is used a lot on guns I don't think the parts grow much, The toleranses on weapons is pretty close so that should not cause problems.
Nothing is impossible, it just take more time to figure out.

Offline redshift

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Re: Parkerising technique
« Reply #12 on: September 28, 2013, 01:39:39 PM »
As it happens I will be doing a few items at the back end of next week , I will measure carefully
and report back.
Regards
Dave

Offline Pete W.

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Re: Parkerising technique
« Reply #13 on: September 28, 2013, 02:26:44 PM »
Sid & Redshift,

Thank you both.
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline PekkaNF

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Re: Parkerising technique
« Reply #14 on: September 28, 2013, 03:56:03 PM »
Hi there, all,   :wave:   :wave:   :wave: 

Nobody has answered the question in my earlier post - does this process cause the component to 'grow'?  :scratch:   :scratch:   :scratch: 

For example, if the part has a screw thread, do you have to mask it to preserve the fit?
[/quoten]

I haven't measured any samples yet, but one manual says roughly "100C 20 minutes phosphating will make 0,005 - 0,010 mm thick layer" and barel is plugged. Bluing at 150C 30 min will etch 0,001 - 0,005 mm. Phosphating will increase dimensions and bluing will decrease. Now, those are linear dimensions, I would think that threads and edges are more prone to etching...but often corners are starved on additional methods...Hmm :coffee: This needs an experiment. I can not guess it offhand.

Pekka

Offline redshift

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Re: Parkerising technique
« Reply #15 on: October 01, 2013, 01:33:20 PM »
While the cat's away!!!. I have the brew on as I write.
Will know in 20 -30 mins if it worked and will measure any increase in size when it has cooled.
Regards
Dave

Offline redshift

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Re: Parkerising technique
« Reply #16 on: October 02, 2013, 06:25:30 AM »
Managed to finish the first experiment before she got home, the kitchen was sparkling, here is what I finished up with:-




I was somewhat disappointed with the result
1) the colour was lighter than I had expected
2) the finish on the parkerized areas was worse than before the job was started.

 In answer to the question of changes in size before and after here are the measurements and how they were arrived at. I used a reamer which was covered in surface rust and de rusted it in Citric acid and then glass bead blasted it to a clean finish, I then masked part of the parallel shank above the cutting head. The shank measured perfectly parallel as you would expect.
After Parkerizing the masking was removed and the shank was measured.
Here are the results:-

Parkerised diameter... 13.732 mm
Untreated diameter.... 13.758 mm
So in a nutshell, it was opposite to what was expected.
Also if you look carefully, (click on picture), you will see some markings along the length of the teated section these are fine grooves that can be felt with a finger nail. What's all that about as they are not present on the untreated area.

I'll leave it at that for now and have a think before I do some more experimenting
Regards
Dave.

Offline awemawson

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Re: Parkerising technique
« Reply #17 on: October 02, 2013, 11:02:36 AM »
Those are grain lines showing up as effectively the part has been etched. At least it confirms that the grain in the steel lies in the right direction! Possibly a forging to start with before machining, but that could also be grain from a drawing out process.

Andrew
Andrew Mawson
East Sussex

Offline redshift

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Re: Parkerising technique
« Reply #18 on: October 03, 2013, 06:22:22 PM »
Here we go with the second attempt. Andrew put the idea in my head that I probably had used too much acid and had caused the surface
finish problems so I reduced the acid content to 60 : 1 ie. 50cc of acid in 3 litres of water. This was mixed over 5 tea spoons of manganese dioxide and a piece of steel wool about 100mm x 25mm x 20mm. (not very scientific I know but it will do for now).
After a bit of internet reading I decided to let the acid dissolve the steel wool before heating the mixture, after a few mins. fizzing all the steel wool had vanished and the mixture was heated to a simmering/boil.
The parts were dropped in and 20 mins. later were removed and rinsed in hot water.
Result, A lot blacker than last time but still a change to the original surface finish, this time the finish was about equivalent to 600 wet and dry using the thumb nail test.
So at this stage I am thinking less acid in the mixture will have less of an etching effect and may help to preserve the original surface finish.
One question before tomorrow's experiments, are twist drills parkerised?
Regards
Dave

Offline vtsteam

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Re: Parkerising technique
« Reply #19 on: October 03, 2013, 09:36:42 PM »
Thanks for these experiments redshift. The photos are really good. Following with great interest!  :thumbup: :beer:
I love it when a Plan B comes together!
Steve
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Offline PekkaNF

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Re: Parkerising technique
« Reply #20 on: October 04, 2013, 02:29:03 AM »
Your and mine experiments conform few things:
* Too much accid etches. If you look old recepies final accid contents is pretty small and much spent on aging. There seems to be benefit of adding up clean water to replace evaporated water.
* Some sources claim that the water quality is important and copper/zink ions?? chlorins, carbonates or something should be avoided. I have used battery water, but read a lot of pro/con, looks like local water and it's treatment are very differet from place to place.
* Surface preparation and cleanless is very important. Some instructions go pretty deep with sand blasting, even down to sand and air quality.
* I noticed that faster you can process from surface prep, better it is.

Then one variable is this "aging" with homebrewn park. I noticed that that I get better results if the park is brought to boiling point and kind of flaky things start to circulate (Flocking). Then I preheat the piece on "rinse" and then bring it into park to "boil". Can't remember exactly, but I made some experiment with the same metal/park/time ,only changing the temperature a little bit and least on my thermometer under 90C it did not work, and worked between 92-96C.

Industrial parkerizing solutions seems different breed.

Pekka

Offline redshift

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Re: Parkerising technique
« Reply #21 on: October 04, 2013, 05:06:34 AM »
vtsteam:-  Thanks for the comments.

PekkaNF:-   I bought 10ltrs of 81% acid for 30 inc. tax and 1kg of manganese dioxide for 3 inc tax so I think that until I get a feel for the percentages of each I will be better doing a fresh mix each time.
 
    Up to now I have been using boiled tap water. I have a friend who works at the local laser cutting factory who will get me a load of
de ionised water to use (hopefully today) so that should be another variable out of the way.

Surface prep has been Glass bead  blasting to a smooth satin finish and into the mixture within seconds.

Regarding flocking, The mixture is an opaque brown colour and as such I will not be able to see any Flocking. Having said that I notice that once the mixture has cooled there is a thick layer of sediment covered by a clear liquid, I wonder if this will still do the job if I decant it off the
sediment?

I notice also that the clouring is different for different materials so I will make multiple samples from the same material, (a 25mm dia. go kart axle in EN8, don't know the new fangled steel codes), and that's another variable gone.

I don't fully understand the chemistry of this process and I am very confused with all the conflicting information on the net but as I need to be able to do this to decent standard I will plod on until I can.

    Regards
            Dave

Offline Arbalist

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Re: Parkerising technique
« Reply #22 on: October 04, 2013, 06:21:12 AM »
This is an interesting thread, thanks for posting and those that have added to it.  :thumbup:
It's a shame that many "useful chemicals" have become harder to source here in the UK.
I use gun blue for small components and it works well enough but it's too expensive to use on bigger stuff.
There are also blacking kits available but some of the chemicals are given a proprietary name and the price doubles, or triples! Keep up the good work guys!