Thread: Phosphating parts "experiment"

Originally Posted by rob streeper

Wow, I haven't seen a dry-cell in years. I wasn't even aware that they were still made. If you can get them then it should work.

Also a nice source of carbon rod !

In regard to linseed oil on metal: http://www.fullchisel.com/blog/?p=1157

Painting of phosphated surfaces is common (http://www.metcoat.com/phosphate-coatings.htm), so what would be wrong with using PU? Isn't it really just clear paint?

You could also use cosmoline but it's messy and relatively expensive: http://www.cosmolinedirect.com/

Originally Posted by rob streeper

In regards to linseed oil on metal: http://www.fullchisel.com/blog/?p=1157

Painting of phosphated surfaces is common (http://www.metcoat.com/phosphate-coatings.htm), so what would be wrong with using PU? Isn't it really just clear paint?

You could also use cosmoline but it's messy and relatively expensive: http://www.cosmolinedirect.com/

Rob, you are confusing linseed oil and so called "boiled" linseed oil (which isn't "boiled" at all these days and instead has all sorts of nasties in it to make it do what genuinely boiled linseed oil did, but is cheaper to manufacture), while the raw stock is the same, they are effectively two quite different finishes in practice. Raw linseed would possibly be a good candidate, but why the heck you'd want to use that instead of just conventional mineral oil is beyond me. We're constantly flooding our machines with oil, and wipe them down afterward to both clean and protect them. I don't know of anyone who drags out a bottle of raw linseed oil to wipe his machines down with. One thing a machine shop typically has no shortage of is oil! Just take the nearest to you at the time and use that; same same no different!

Yes PU IS just clear paint for the purpose of this exercise. The treatment I've described is Phosphate and Oil finish, it is not phosphating for the purpose of painting or coating with any other film finish. That's really another process and one that could be substituted with things like etch primer etc. or just wiping it down with phosphoric acid! One of the whole principle behind this P&O treatment is that it effectively doesn't change part dimensions (not to an extent we need be concerned about anyway). Threads, features, etc can be used just exactly the same as prior to treatment, and the same can't normally be said for films. There are many other advantages to P&O, one of the main ones in industry is the reduction in friction etc when first using parts like gears etc. My main interest however is in providing a suitable means to colour and protect workshop tooling.

Cosmoline would be a poor choice of oil, mainly because it's not. I spend enough time removing Cosmoline from parts without adding more to parts I'm going to be handling every day!!! I think some are latching on the the term "sealing" and trying to convert that to something they're more used to in other fields. The coating is very thin and the crystals forming it are like a sponge with holes in it. The oil comes along and just fills in those "holes". That's it, the coating is now sealed. Since the holes are so incredibly small, the oil effectively can't get back out again. Oxygen can't get it and water has no chance. IF it was left exposed for a very long period of time and the oil eventually dried off, then I presume the part would be the exposed to corrosion again, but I've been unable to ascertain just how long that would take s accelerated corrosion testing won't capture that. It will be a "long time" however in a workshop tooling environment.

Look guys I'm sorry to sound frustrated, but I genuinely am. I thought I'd post this up as the whole concept is quite simple, very VERY cheap, and accessible to anyone. By all means if you've been doing this for a while, done some experiments of your own, and developed ways that you've found for yourself are more suitable for your own needs then please share them, that's what this forum is all about and I'd love to learn from them. However I don't mean to pick on anyone, but a number of comments here have had me slapping my face wondering why I even bothered to post it! Having never tried it, some seem intent on "suggesting" better ways of going about things!!! I make no claims of anything new or revolutionary in what I put up, all I did was waded through a boat load of BS on the internet, tried to sort some wheat from the chaff, and simplified some commercial processes I knew about to remove many of the chemicals that we'd probably have more difficulty in obtaining. That just leaves 3 things to find, and they're not difficult or expensive to get. 4 if you count the water, open a tap for that! Phosphoric acid, manganese dioxide or zinc, iron or steel wool, then finish and seal it with bog standard mineral oil. That's it. I'm even extremely dubious about the need for that iron source, and would like to try the next batch without it at all, especially in things like aluminium and brass, which it also is supposed to be effective on. No wheels need be invented here, it's simple, it's cheap, and the solution is only mildly acidic, so is relatively safe IF you use common sense (compared to say boiling caustic solutions etc!). There's no need to take chances with your health to save pittance in material costs, the cost to do each "brew" is only cents anyway. The materials are very easy to find too. Just order them off ebay. I'm sure there are local sources for pottery suppliers too. You may have to make adjustments to the amount of phosphoric acid you use if the one you buy is other than 300g/l that I used in my recipe, it does however seem to be a common strength.

Good luck with it and let us know how you go.

I for one am very thankful you posted this Pete, despite what has been said. As you know i'm not just looking for finishes for a few things round the shed, but for small production hence my going to Caswell's kit. However it is very expensive and i have been disappointed at just how few parts (well a few hundred but they claim a huge surface area can be finished with the kit, far more than i have done) i have done and it has run out of "black".

The heat has me a little concerned, but i think an old electric stove, thermocouple, controller and SSR might be the smart way to set it up for easy long term use.

Thanks again,
Ew

I'm with Uee, I agree this has been a most interesting and useful post.

Originally Posted by Pete F

Rob, you are confusing linseed oil and so called "boiled" linseed oil (which isn't "boiled" at all these days and instead has all sorts of nasties in it to make it do what genuinely boiled linseed oil did, but is cheaper to manufacture), while the raw stock is the same, they are effectively two quite different finishes in practice. Raw linseed would possibly be a good candidate, but why the heck you'd want to use that instead of just conventional mineral oil is beyond me.

I think the cross wires here are because the original experiment was on a truck tray hinge, so some folks (well, I know I was) may be thinking more general - especially outdoor - uses.

The reason for using BLO as opposed to mineral oil on an outdoor use would be because it polymerises and forms a semi-hard coating where mineral oils are less likely to do this. BTW most plant derived oils will, eventually, polymerize. Canola oil is sometimes used in chainsaws because it may be cheaper than conventional bar oil but leaving canola in a saw for some time may end up with all the oil lines clogged. I have used it on the auxiliary oiler on a chain saw mill and the canola has made a real mess of the bar nose end of the chain saw mill so I have switched back to conventional bar oil.

RE: PU coatings
For outdoor (especially here in Oz) purposes the PU (or any clear coating) will eventually yellow and then turn cloudy and look pretty ordinary.

Back to the original experiment, I would be interested to know how the process differs from deliberately lightly rusting the work and then using phosphoric acid to convert the rust (oxide) to a phosphate. The emersion in a liquid will have the benefit of better penetrating gaps etc but the end process is from what I can see an iron phosphate layer over the objects that slows down rusting.

I guess the real question is how much manganese or zinc really gets incorporated into the iron phosphate layer.

Back to the original experiment, I would be interested to know how the process differs from deliberately lightly rusting the work and then using phosphoric acid to convert the rust (oxide) to a phosphate. The emersion in a liquid will have the benefit of better penetrating gaps etc but the end process is from what I can see an iron phosphate layer over the objects that slows down rusting.

I guess the real question is how much manganese or zinc really gets incorporated into the iron phosphate layer.[/QUOTE]

Bob,

You can Parkerize over oxide blues, including nitre/rust blues, with no problem. I recall many years ago having one of those cold bluing kits with the selenium oxide bluing agent that also had a bluing remover which by the way was phosphoric acid. I used it once and it left a dull but definitely clean metal surface. Acetic acid at concentrations higher than vinegar will also remove rust blues, had a buddy who tried to clean the copper out of the barrel of his Winchester 52 target with acetic acid and stripped the blue right off. Don't want to go too far off topic so I'll bail out on this for now.

Cheers,
Rob

Originally Posted by rob streeper

. . . .You can Parkerize over oxide blues, including nitre/rust blues, with no problem. . .

I wan't think of Parkerizing over a blued material, but a very light rusted material.

I read up a bit more about the chemistry of Parkerising and it appears that although the end product is the same Parkerising is different

Phosphate Rust conversion with Phosphoric acid is effectively
Fe₂O₃ + 2H₃PO₄ → 2FePO₄ + 3H₂O

While parkerising is
2 Fe(s) + Fe₃+(aq) + 3 H₃PO₄-(aq) → 3 FePO₄(s) + 3 H₂(g)
In practice I can't see why any rust on a surface to be parkerised won't be converted to phosphate, as would an exposed layer of solid iron on a rusted surface treated with rust converter.

I suspect the main difference is that the Parkerising bonded layer of phosphate directly onto the metal substrate is mechanical superior to the phosphate layer produced by rust conversion.

BTW I'm not talking here about rust conversion of a thickly encrusted rust layer but a deliberately induce layer of very fine rust.

That's why I mentioned rust bluing as really it's just the finish left after a series of controlled rusting and wire brushing steps. My feeling is that the iron oxide surface would just fall off as fine particles and or the phosphoric acid would take it off. I wouldn't predict any effect on the Parkerizing unless as, you mention, the rust is thick.

Pete,


Thank you for the comprehensive documentation. I do like the idea of using the phosphate as a means of providing paint adhesion.

I walked away from the kitchen stove because I wasn't achieving the intense black I was hoping for when I had a go at "Parkerising". Never thought of using a die for colouration.

The application of oil blackening over the phosphated iron did work however - https://www.woodworkforums.com/showth...06#post1208606 but the use of heat and its temper changing property was the reason for me dropping the $180 or so on the Blackfast kit. I'm still using the mixed up solutions from when I purchased the kit back in 2010. The advantage of the Blackfast setup is that I can blacken one single small part such as the other day's little dovetail clamp easily and quickly. And the white tile grout isn't at risk.


BT

I really did go to quite some lengths to emphasise that the "crash test dummies" I used on this Hilux were simply because they offered something to test them on. The whole process is not intended for eternal use, and I honestly don't know how I can make that any clearer, but I chose an application that did indeed have them outside so as to see just how they held up anyway, and just how long it would take for the coating to break down. So if, just for example, in 12 months time they're sitting there without rust, there's a good chance they're going to protect our workshop tooling ie the intended purpose. If on the other hand they begin rusting after the first shower of rain, we may have to rethink all this, but I strongly suspect that won't be the case. For external use you'd use this process and NOT oil them, and instead then add your film coating. I have some outdoor things I intend doing for example. I was intending to zinc phosphate them, but I'm leaning more toward manganese now, but either way they'll then be powder coated.

With regard rusting of the parts, the rust bluing is a different process, although is indeed a conversion process, it basically converts the metal on the exterior from a layer of rust (now let's see if I can get this right, Fe2O3) to a fine layer of magnetite (Fe2O4). Obviously then it only works on things that will rust. From what I read at the time, rust bluing may well be a desirable aesthetic finish, but offers minimal protection. It's also extremely time consuming, even if accelerated. In the phosphating process the phosphoric acid is very weak, we're basically taking an already diluted phospharic acid mix (approximately 300g/l) and then further diluting this around 15 times!). This brew is really only very mildly cidic and the role of the phosphoric acid in converting rust to Ferric Phosphate would be minimal if mixed to the recommended strength. You could however use it undiluted to remove rust before beginning the phosphating process, however just be aware that these are two independent processes. The items should therefore be de-rusted before phosphating.

Bob what I described is "Parkerising" indeed you can go to the original Parker Rust Proofing company in Detroit and see they're still doing the same thing. Possibly one of the last remaining companies still IN Detroit from what I hear. They promote either zinc phosphating or manganese phosphating. The former is Zn3(PO4) and the latter is Mn3(PO4)2. What you've described is, I believe Iron Phosphating, the third of the phosphating options, but from what I read, one only really suitable for a subsequent film finishing. I haven't set out to deliberately replicate this process as iron phosphating, but anyone who has prepped sheet metal say for painting would be aware of this process, as if using something like the 3M rust converter before spraying, you really need to get the primer on there quick smart, as the steel is exposed and will start to "flight rust" reasonably quickly.

Ewan I hit K-Mart up for the hotplate and a suitable SS casserole dish. Having a lid is handy as you can lose a surprising amount of liquid to steam, even if you keep it below boiling. Neither were very expensive, and I figured the hotplate would be a handy heat source for other things in the workshop. I can't recall where I got the thermometer, but almost certainly the same place. One of the few things K-Mart is good for these days in my opinion!

Bob, yes I too have tried oil blackening over manganese phosphate, and it worked ok, but I have never liked the oil blackening as a process. It truly stinks and just isn't a friendly approach in my opinion. After the last time I tried it I thought afterward about using dye, but this was the first attempt at that. I went through a couple of dozen MSDS from different manufacturers at the time I first tried this, a lot of them are very similar, some are different, it just depends on the blackening process they use. The use of dye was clearly used in one manufacturer's process however. I love MSDS as they cut through all the BS and companies can't hide. Occasionally you'll see something that will say "trade secret" but it's rare, and I only recall one off the top of my head (in this field anyway).

Careful with the lid Pete, some of the bubbles are hydrogen. Capture and ignite it and things could get interesting. You may see better results using the 'distilled' water sold in grocery stores depending on the calcium hardness of your local tap water.

I also would like to add my thanks for your explanations Pete. I would find this process useful.

Dean

Originally Posted by Ueee

... it has run out of "black".

The heat has me a little concerned, but i think an old electric stove, thermocouple, controller and SSR might be the smart way to set it up for easy long term use.

Ewan I just re-read your comments again, regarding the black I'd try the similar dye I used if you needed to top up the black in that kit. Indeed I'd check the anodising type dyes, as I think these processes would take up any of the dyes used in anodising from what I saw. Obviously the hue of the phosphating process used will limit the ability to use any lighter dyes, but certainly if going for black you should be ok.

As far as the temperature, I may have overstated it a little by saying it's relatively "critical". In fact what happens if it drops below the high 80 C the process just slows down and almost seems to stop. Conversely if it's too high it begins to boil, and you lose too much water. However anywhere in the low 90 C range and you'll be sweet. I find the standard hot plate thermostat does a good enough job, however unlike a PID it of course isn't smart enough to learn the behaviour and characteristics of what it's controlling, but so long as you anticipate reasonably well when you first heat it up, once it settles down it maintains the temp within a degree or so (as least mine does, and trust me it's nothing special!). I think I have a spare PID laying around here somewhere, but I wouldn't waste it on this.