Thread: Phosphating parts "experiment"

In regard the above recipe, I don't know how critical those figures are, other than the acid. Manganese is certainly not soluble, and sits there in a sludge, likewise there's always iron/steel wool or excess zinc that isn't dissolved. Whether it would be eventually I don't know, I'll need to do further experimenting in that regard.

Here's a photo of some steel wool for those who can't remember what it looks like.

Steel wool.jpg

Put the acid, water and zinc in a stainless steel pot and bring it up to 92 degrees (ie just below boiling). The temperature is reasonably critical, and if it's too low it won't work, if it's too high it will boil and evaporate too quickly. When you add the steel wool or iron you'll get a lot of foaming and carrying on.

Acid and zinc.jpgAcid zinc and iron.jpg

This is the thermometer I use, it's next to some pliers I used here to swish things around and retrieve parts. You can clearly see how the tips of them are zinc phosphated.

Thermometer.jpg

Pete have had as many scotch's as me?? Good write up so far.....

Ew

Come on Peter. Don't leave me hanging............ Next update please!

simon

Here's a before shot of the parts. As mentioned, absolutely no prep, and there's even still some rust on them. Sorry Mr Toyoda, care factor zero.

Parts before.jpg

Eventually the foam will subside and at that stage the brew is ready. I keep swishing things around to make sure everything is as dissolved as it's ever going to be, and reduce the foam as quickly as I can. Maintain 92 degrees by keeping an eye on the temperature.

Ready to brew.jpg

Put the parts in and you'll see small bubbles forming around the parts, they bubble quite a lot, but aren't exactly frothing. Sorry I forgot to rotate that photo before posting, but if you look roughly in the middle of the bare area you can see one of the parts bubbling just below the surface. It's one reason you don't want too much foam around, as you want to be able to see the parts. Eventually the bubbles will slow down and preferably stop completely. If they don't, then you probably thought you knew better, added too much acid, and the parts are being etched. It should only take about 5 -10 minutes. If you've done everything according to the above and they're still bubbling after 10 minutes whip them out, as they probably won't stop .... and you used too much acid! Not to worry, they're probably plated ok anyway.

This is what they look like when they first come out. This is one thing that's different with the zinc, as the manganese, apart from being a different colour, doesn't have those white patches. I suspect lack of surface prep is the cause of them. They're still a little wet when I took the photo.

Parts after.jpg

At this stage the phosphating itself is complete, however the real magic is to follow.

At this point the surface has a distinct matt texture feel to it, I quite like the feel of it in fact. You can just feel it if you rub your thumbnail on it (fingernail if you don't have opposing thumbs), apparently like a lot of the people who write about parkerizing! More the point however is that it's like a sponge ready to accept whatever is put on it. If it's paint/powder coat it will stick like $%^& to a blanket! Well, unless it's one of those petrified white dog turds, they don't stick to anything. Why are they white BTW? I'll save that for Crazy Science 102. Anyway we're not going to do either, paint is too good for this bucket of bolts. What I want to try is to see if a phosphate finish will take up black dye. Bob does some great blackening but he uses a process that costs money. I'm Scottish* (nice pickup Ewan) so don't like spending money. Ever. There's no way as long as my butt faces South I am going to spring for a fancy nancy blackening kit, soooo, out with the black dye. The can should give you an idea of how old it is, rumour has it Noah used it for the arc details, but I can't confirm that. As soon as the dye hits the surface it soaks in and spreads out like crazy, it just looooves phosphated surfaces it seems.

*Actually I'm not Scottish, but should be!

Blackening.jpg

This is what the 3 parts looked like after blackening. Oh I forgot to mention in my last post, just rinse the parts in water quickly and then dry them off with a heat gun. They should then be dry and ready to accept finish.

After blackening.jpg

However at this stage the "pores" of the surface are still open, so it needs a final step, and that's a coat of oil to finish them. I understand that even when exposed to weather, the oil is basically embedded so far down in to these "pores" it will just stay there and protect the part. Everything up until this stage has gone to plan and is what I expected, but what I didn't know is what would happen to the dye once oil hit it. Would it just bleed out and get washed away by the oil? Dunno. Only one way to find out.

After blackening and oiling.jpg

In fact there was no bleeding or other changes to the dye whatsoever. Now keep in mind I don't know how UV stable this will be in this instance etc etc, the whole point wasn't to somehow recondition those parts, rather it was just to show the process and also for me to see how it weathers in reality. Even my 5 year old daughter nags me as to why I never wash my ute (I fooled her and both washed and polished it the other day!!), so it should be a pretty good test as to how the process will hold out.

The final 2 shots are a close up of the part (you can see how it really needed prep) and back on the vehicle, together with a before reminder. You can clearly see I haven't wiped all the excess oil off in the first shot.

Finished part.jpgFinished on vehicle.jpgHilux before 1.jpg

In fact I will strip the parts off this vehicle one day, clean them up, and may/may not phosphate them, we'll see. The main reason I use this process however is to finish workshop parts however hadn't ever tried the dye before. I'll say that was 100% success, and I'll blacken my parts using it in future. I've heard some say that you can't re-use the brew, I've done so in the past and see no real reason why that should be the case. I've thrown it out before but now I'll keep some handy just to be warmed up on the hotplate. It's highly likely however that the acidity may need to be tweaked if it's reused, however it should be obvious that there's no reaction or it's delayed. A smart guy might test the ph and go from there, lucky no ph kits are in danger from an idiot like me!

For those who want to read further, I would suggest this as one source http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA018131 otherwise gun finishing books would be good. However in all honesty, as mentioned I'm certainly no expert in this, but it's not rocket science. Here's a picture I grabbed off file of a manganese phosphated washer next to one that's raw steel, you can see the distinct brown hue to it when compared to a commercial lathe tool and holder. However that hue should be eliminated with dye.

Manganese Phosphated washer.jpg

That's all there is to it, nothing much else to say on the topic that I can think of. Good luck and enjoy!

Edit: Oh I forgot, one thing I did notice is that this zinc didn't seem to be as durable as the manganese. I know it's only N=1, but the finish seemed easily scratched by the tools of putting them back on the vehicle. It really is very thin, but the manganese seems more durable in this regard. Mind you, if it were thin paint it would probably have been scratched just the same, but thought I'd add that observation.

Originally Posted by Pete F

However at this stage the "pores" of the surface are still open, so it needs a final step, and that's a coat of oil to finish them. I understand that even when exposed to weather, the oil is basically embedded so far down in to these "pores" it will just stay there and protect the part.

Interesting Pete.
Previous employers have used phosphating as paint prep, as it works very well and is cheap (car parts etc). The important thing is those pores - if water gets into them eventually you will have rust, so the dye/ oil treatment or paint is a must. Like grit blasting you are meant to prime within a few hours of the treatment to avoid problems. I don't know how long the oil will stay in there, so that might have to be the long term test. We did use phosphating on military vehicle parts but only those that would be be wiped down regularly with an oily rag (eg weapon mounts). External vehicle parts would be painted - this is all second hand knowledge and as you say may be part of the BS that surrounds the process so I'll be interested to see how durable it is.

Michael

Thanks Pete.
Unlike you i am Scottish* and unlike you i bought a kit from Caswell as i had a s#%t load of parts to black NOW!
The price of the kit is not too bad but the price they charge for TNT dangerous goods transport is ridiculous.
Crazy as i get DG goods from Sydney pretty regularly at a fraction of the TNT cost.
I think i will have to have a play with your above recipe, it will save me $$ and if what i have read is true (it was on the internet....) it will be tougher than the copper selenium black, which is a deposition method not actually an oxide at all.

One thing i have noticed with the CuSe is it takes far better on a rough surface (read sandblasted) than a ground surface.
The local knife guys want to try the CuSe on damascus, i might try to get a blank and try the zinc on it.

*Also unlike i have really had too many Scotch's and typing is hard.....

Ew

Pete, thanks for the great write up, will try it out when I make some more tooling for myself.
Kryn

G'day Michael, yes I agree, the process is only half done once they come out of the bath, and the oil treatment is essential (unless of course it's to be painted). I can't recall where I read it now, but I'm pretty sure I recall a credible source stating that the oil basically soaks so deeply into the pores that it's essentially not effected by water, detergents, etc. I guess a little like oil soaking in to concrete, except on a smaller scale. In salt spray testing (accelerated corrosion resistance testing), the paper I linked to above was indicating >1000 hours. That used to be the maximum, no idea if it still is but presume so, regardless it's very good.

The main thing I'm interested in it for however wasn't outdoor use, and I'm really only curious as to how it stands up in that regard. Rather it's for workshop tooling, where I require a black finish, quite like the texture of P&O (phosphate and Oil, the technical term for this finish), and cannot tolerate any dimensional change in parts with finishing. In fact I'm probably as curious about the UV resistance of that dye I used as much as the weather resistance of the whole thing. Whether stains would be suitable I don't know, but doubt it.

I'm just reading again, you don't mention the sort of oil you used?

Ew

I honestly don't think it matters Ewan, I know a lot of people use WD-40 as it's moisture displacing, but I think it's cat's wee. Instead I just happened to use hydraulic oil, ISO 32 to be precise, as it's what I had in the nearest can. WD-40 probably makes more sense for indoor tooling, but I couldn't see that lasting too long in this application and wanted to give the thing half a chance of success. The pores really are tiny, but I doubt the oil viscosity would affect things. To give it an even better fighting chance however I heated the part somewhat first. In other things I've done I used engine oil, but hadn't tried the dye, so in one case actually oil blackened the phosphated parts. It seemed to work well, but of course stinks. For tooling in future I'll probably dye it, then WD-40 despite my opinion of it. Maybe follow with conventional oil, but by that stage I suspect the pores will be sealed.

Obviously if you're going to paint or powder coat don't apply the oil, or anything, just phosphate it and you're good to go. The dye however is freakish to watch it go in, it almost want to leap off the cotton bud and get in there by itself! It basically touches the surface and spreads out like all heck, but then doesn't rub off. Quite freaky!

Finally, I've tended to use lay terms throughout, but upon re-reading it, I think it may lead to some confusion, at least potentially. The main thing is when I say "coating" or "plating" etc. In fact technically it's neither, and I believe phosphating is technically considered a conversion process, where the outer layer of material is converted and there is little dimensional change in the process. There are in fact 3 different phosphating processes, the third is iron phosphating, but I've never tried it and it doesn't appear as popular as the other two.

I wonder how Penetrol Paint would work as a sealer..

The sealer that comes with the caswell kit is very thin, and smells somewhat of crayons. Not sure what it is.

One last thing (for now) Pete.....how much zinc did you use?

Ew

10 g of zinc Ewan, as per recipe. So just to clarify that, you use either 10 g manganese OR 10 g zinc, not both. No idea of what would happen if you use both.

However I was just laying in bed when I realised I'd forgotten to mention a fairly important safety point. I don't smoke so it didn't occur to me. You shouldn't smoke either ... it's bad for you ... give it up. But if you do choose to smoke around this setup you might be giving it up a lot earlier than you'd planned, as it produces loads of hydrogen when you introduce the Fe to the acid. Indeed the little bubbles on the part being phosphated are hydrogen bubbles, so don't have any ignition sources around it. I believe there is another ingredient that you can add to it that causes a reaction such that instead of H2 being produced, H2O is produced (presumably it's then some type of oxidiser but I can't for the life of me recall which one. I did all this reading a number of months ago now). It helps to speed up the phosphating as the hydrogen bubbles effectively block the process. However even if that were used, I would treat it as if hydrogen is there by the Zeppelin load.