I don't know about the coating but the carb sure looks nice. I used to rebuild the quadrajets many many years ago and they never looked like that. Very nice.
Great video Mr. Demes. Not many folks can just extemporaneously perform a task like this while clearly explaining what they are doing like you have done. Very professional and great speaking voice. I learned a lot and I am going to give it a try. I will make one change. After cleaning and degreasing, I am going to Try preping the parts with Muriatic Acid which is dilute Hydrochloric Acid, then rinse well, and see if that will give them a fairly uniform etched surface. Then I will Parkerize.
The Parkerize chemicals sold have a pre dip to even out the color and even out the color on different types of metal. EPI has great chemicals for Parkerize but they are pricey. The home brew is just a way to o it on the cheap. www.epi.com/phosphates/steel/#e-prep-b-3 Thanks for watching.
Thanks for this educational video Harold, and all the efforts for making your instructional videos. I am rebuilding a Rochster Q-Jet #7045275 right now and this comes in real good.
Harold, have you tried just using the clean and etch on the bare metal instead of blasting it as part of your prep? It seems the parkerized finish is a reflection of the surface. If the surface has a different sheen from different grit, the parkerizing will reflect that.
Just a thought,when wet soda blasting the soda is mixed with water until saturation level is reached,then the actual soda for blasting is added,which sounds strange,but the water can't absorb any more soda as it(the water) is "saturated with soda" so adding soda creates a gritty slurry that will remain gritty and so more soda added will not dissolve into solution. SO, I'm thinking maybe the fluid solution is saturated with the manganese dioxide and can't dissolve any more ,unless you add more water. Just a thought from other situations with solution/dissolution processes.
Thank you for a very informative video Harold! I just received both the manganese dioxide and the phosphoric acid i ordered on ebay two weeks ago. Before i start the process of mixing the ingredients i want to hear if you got a suggestion for a recipe using 85% by weight phosphoric acid?
That phosphoric axis is great for doing auto body restoration. Clean that rusty panel then spray it let sit and wash off then wipe dry. wipe dry. It will form a light dark shade on the bare metal and keep the rust pits from activating later on. Great stuff.
I get a black coating but it rubs off and the colour of the metal becomes slightly greyinsh when dry , but when in contact with WD40 it looks black.. the bubbling never stopped even after 30 min ...... how long to keep boiling
Hi Harold, Love this video, thanks for making it. Just one question.... you mention that you normally wait 10-15 minutes for small parts. How long would you wait for something larger like a hood hinge?
Keep it in until you get the color you want. Some metals will only be lighter than others. Depends on the material. To make all different types of metal take the same you need to use a pre dip like EPI E Prep 258
Thank you for this great video. Just gave it a go and the bolts came out like new. Now back to the sandblasting cabinet to do the other 399 bits. Any idea what to soak them in after the parkerizing? Somebody told me that when WD40 is evaporating, it actually attracts water (???). Maybe some kind of gun oil? Thanks again, great information!
go to caswel a company that sells plating chemicals and all the supplies, they have a clear coating to use over zink or phosphate coatings to protect them.
What would cause the solution to turn out more of a yellow like beer? Is this actually ok? I wanted to ask first before I tried a sample part. Just incase it was something simple. I followed everything exactly.
Excellent. I appreciate the detail you put into your instructional videos. I've been using cold bluing to get a similar appearance, but the manganese phosphate appears darker--more of what I am looking to achieve. Definitely going to give your method a try. One question: since you have a zinc plating setup, have you tried the Black Chromate process? Curious how that would compare in appearance and corrosion inhibiting. Keep the videos coming!
Hi Cory I received a sample of the Black Chromate from my chemical supplier about 1 year ago. I think they send me stuff to try because they consider me a Lab type plating operation. It was a good product. I just don't have a customer base for it. I like to try to reproduce the factory finishes. I hate painted fasteners. On car restoration all your fasteners should be plated or Phosphate coated in Manganese or Zinc. I hope this video helps guys doing there own project to be able to do this in there garage. I am working on a Zinc Phosphate home brew. You can buy this chemical form Palmetto Enterprises. It very good. I think about $55.00 with shipping to make a gallon.Thanks for the input. Harold
Is this a concentrate or as is? If you get this message please let me know. I am going to be parkerizing some parts tomorrow. I followed your recipe and it looks great. Thank you sir.
I used atomized iron. The same weight of 1/3 of a steel wool biscuit. My parts are looking extremely dark, but as soon as I rinse them off, the black coating comes off and reveals a very light gray (lighter than zinc phosphating). Any clue what could be causing this? I figured the powdered iron would work just fine. I’ve seen it used in other recipes.
I've attempted to use the recipe and procedure twice, and have failed twice. First time, final concentrate looked like beer, -yellow. seconds time it's kind of purple. I think I'm using too much manganese. Is it two (2) teaspoons manganese, or 1/2 teaspoon? In video you use 1/2, at what point did you add the remaining manganese? It could be I'm having difficulty maintaining temp, as my current thermometer sucks...
Get a candy thermometer at Walley World. Too much Manganese Dioxide will not hurt. You will leave it in the bottom of pan when you filter it off. You can use a full biscuit of steel wool. Has to dissolve completely. Let it cool and settle over night. Filter in a gallon jug and top off with distilled water. It should be a light green color and clear. As you use it you will get evaporation so you have to keep adding distilled water to keep level up as you are using it. let me know if it works out.
When You say You use only distilled water, because of the minerals and salts in tap water - do You think de-ionized water would be good enough? Thamks for another interesting and good tutorial video! ;)
Deionized water is more purified than Distilled H2O. More purity == more $$$. Yes, it would work, but is it worth the extra cost? Depends on your application and quality goals, yes?
Your black oxide video of "metal parts" is no longer on CZcams is that still available via private link? I bookmarked that because how good the information was.
@@backnine. I have searched and searched and searched for the last six months and while I have read many articles, nothing is as information packed as your videos for the DIY'er. Could you post a link to the video on something like Google Drive or Dropbox and post the link here or PM me with the link? Do you have any other videos that were taken down? There are several books on the subject like Angier, R.H. (1936). Firearm Blueing and Browning but they are not as good as your video. I've downloaded everything I could find that was still up on 5/23/24 but like I said your videos are excellent. A picture or video is worth a 1000 words. Please consider one of the options above or can you try re-posting. Thank you SO much
MnO2 dissolves in H3PO4 painfully SLOW. What you are depositing on those parts is iron phosphate and very little is any at all manganese phosphate. You either have to use KMnO as an oxidiser to increase dissolution of MnO2 or you need to add Mn in some other form like metal Mn or Mn-carbonate. You can also add some form of nitrate to sequester hydrogen and accelerate deposition rate. Adding too much nitrate will have an adverse effect. Target ph should be around 2.75 and free acid to total acid ratio somewhere between 6 and 10.
I was surprised to see how much Mn was remaining, undissolved...it did look very much like the small teaspoon wasn't consumed...good suggestions for improving the consumption of Mn.
Hi Harold I am have grave difficulties with getting the solution to work, I have available 98% Phosphoric Acid i have tried to dilute the acid to 50% but i just can't get the solution to look or work like yours does. For some reason my solution is all brown once finished cooking, the acid is clear too start with. The cooking pot has a ton of scum around the top which i notice yours does not. Please help.
How would you prepare machined parts that have coolant on them before parkerizing. I manufacture lots of specialty small parts that we now pay big dollars for black oxide finish. We really want to set up this up to save black oxide cost, shipping cost both ways and faster delivery time to our customers. Any help would be appreciated. We have discussed using this process many times.
You can clean the parts with mineral spirits to remove oil. Then bead blast the parts with a 140-170 mesh glass bead. This beat blast is very fine and will not effect tolerance. then use process in the video. If you want to use Black oxide room temp go to EPI web site. They sell instablack 333. Very good product. I have a video on the black oxide doing a gun.
Great video. I followed your recipe but I got a grey finish instead of black. Not a real big deal but wondering what you think could be the reason i got a grey finish instead of black.
Thank you for the quick response. It was a heat treated piece. Still covers though and looks good. Thank you again. I looked at other guys recipes on here and yours was the best I found. Appreciate the time you put in to making the video.
When I went in the army in 1976 they issued me a depot new old M15E4 or M16E4 I forget which. That pup was OLD likely an early experimental or trial model from the early 60s. When I got it it liked like new cermacoat. My 45 Colt was the same. Those puppy’s were so rough they would scuff your knuckles but smear some oil on and it was IN There. Beautiful weapons and both a nice light to mid gray. That stuff was TOUGH too. I never saw that parkerized finish on any of my issued weapons again, they were all black.
At 17.28 the author makes the comment that "The solution seems to work better the 2nd time around.", could this because it is lacking in iron? Maybe more steel wool should be added initially.
So your mix once topped off with distilled water in a gallon jug is ready to use? No need to mix with more distilled water when filling the parking tank? I have a project that wasting a few bucks to make this could save me alot of $$. I was told to wrap a steel wool pad in a coffee filter and submerge it in the tank for at least a half an hour to activate the solution. This might cure the poor covering problem you have on initial parts. Thanks for sharing.
You could put more steel wool in the initial mix it will not hurt any thing. As I said for the car restoration stuff it works great and cheap. You have to keep adding distilled water when you are heating it to keep the level up as you get a lot of evaporation at that temp. I just did a AK47 to try the solution. Most of it came out jet black but the forged parts came light. The guys that sell the park solution have a predip that suppose to solve that problem. You will see that on some fasteners on car parts also. I am trying to find a predip formula and if it works out I will do a add on video. When you are done just filter it put it back in a jug and top off with distilled water and keep using it. It last a long time. You can buy the the pro stuff but the Hazmat fees are killers. Post your results.
I've had AR15 barrels that look lighter like that. I cheat and rub them down with black moly grease and heat them up with a propane torch, then wipe off the excess. good protectant and darkens it too.
I knew the different metal would be a problem on the gun. The receiver on the AK I plug welded the rails and the park took light on the weld circles (not bad) but you can see it. Also I spot hardened the FCG holes and some other high stress areas and they came out about a shade darker. I will paint this one with duracoat to even it out. The Park will be a good primer + when you park it it gets into all the areas paint won't get. I am starting another AK and bought a fully hardened 80% receiver and will spot weld the rails. I may buy the the predip and try some parts with the home brew and post a result. What makes the park bite good is to media blast the parts. I use a 100-400 mesh glass bead it real fine.
@@backnine Sandblasting is a key issue here. Also, make sure after sandblasting you never touch the part again until you are finished. After sandblasting soak the parts in brake cleaner or acetone for 20 minutes. But never touch the part again until you are done... meaning if your last step is parkerizing then remove your part from the tank (with gloves on) then oil it up. Then you can touch it with bare hands. If your last step is a tactical coating then do not touch the part with bare hands until you have painted the part and it has been cured... oven or whatever.
I saw another video where the guy had a purchased kit of chemicals that included a pre-dip. He said the pre-dip smelled like muriatic acid. Muriatic acid might etch the surface of the part and make it more receptive to the manganese phosphate
Your finishes come out splotchy because you are touching the pre-finished parts with your bare hands. You are getting skin oil on the surface so the manganese is not adhering evenly. Use your gloves for all steps, and your finishes will be more uniform. Thanks for sharing!
I find I get the best finish adhesion by washing the parts to be coated in soapy water, rinse and dry, and give them a microetch in muriatic acid for 30 seconds to a minute, re-rinsing, and finally submerging in solution by a thin wire hanger.
Love it when someone takes pride in his work and has spectacular results!
Professional results on dollar budget!
Thanks for the video! I followed it and successfully parkerized some motorcycle parts today. It really works!
Another great video.
Thanks for sharing.
Thank you sir.
Formula worked perfectly 🤗
I don't know about the coating but the carb sure looks nice. I used to rebuild the quadrajets many many years ago and they never looked like that. Very nice.
Great video Mr. Demes. Not many folks can just extemporaneously perform a task like this while clearly explaining what they are doing like you have done. Very professional and great speaking voice.
I learned a lot and I am going to give it a try. I will make one change. After cleaning and degreasing, I am going to Try preping the parts with Muriatic Acid which is dilute Hydrochloric Acid, then rinse well, and see if that will give them a fairly uniform etched surface. Then I will Parkerize.
The Parkerize chemicals sold have a pre dip to even out the color and even out the color on different types of metal. EPI has great chemicals for Parkerize but they are pricey. The home brew is just a way to o it on the cheap.
www.epi.com/phosphates/steel/#e-prep-b-3
Thanks for watching.
Great Video!!!
Thanks for this educational video Harold, and all the efforts for making your instructional videos. I am rebuilding a Rochster Q-Jet #7045275 right now and this comes in real good.
Harold, have you tried just using the clean and etch on the bare metal instead of blasting it as part of your prep? It seems the parkerized finish is a reflection of the surface. If the surface has a different sheen from different grit, the parkerizing will reflect that.
Was it a half a teaspoon or two teaspoons of manganese dioxide?
Just a thought,when wet soda blasting the soda is mixed with water until saturation level is reached,then the actual soda for blasting is added,which sounds strange,but the water can't absorb any more soda as it(the water) is "saturated with soda" so adding soda creates a gritty slurry that will remain gritty and so more soda added will not dissolve into solution.
SO,
I'm thinking maybe the fluid solution is saturated with the manganese dioxide and can't dissolve any more ,unless you add more water.
Just a thought from other situations with solution/dissolution processes.
Great video info. Did you park the pistol?
would holding off on the iron addition help eith manganese disolving maybe?
do you know what the iron is for?
Thank you for a very informative video Harold! I just received both the manganese dioxide and the phosphoric acid i ordered on ebay two weeks ago. Before i start the process of mixing the ingredients i want to hear if you got a suggestion for a recipe using 85% by weight phosphoric acid?
That phosphoric axis is great for doing auto body restoration. Clean that rusty panel then spray it let sit and wash off then wipe dry. wipe dry. It will form a light dark shade on the bare metal and keep the rust pits from activating later on. Great stuff.
Can u tell me please how to make cold zinc phosphating chemicals?
I get a black coating but it rubs off and the colour of the metal becomes slightly greyinsh when dry , but when in contact with WD40 it looks black.. the bubbling never stopped even after 30 min ...... how long to keep boiling
Very good
Hi Harold,
Love this video, thanks for making it. Just one question.... you mention that you normally wait 10-15 minutes for small parts. How long would you wait for something larger like a hood hinge?
Keep it in until you get the color you want. Some metals will only be lighter than others. Depends on the material. To make all different types of metal take the same you need to use a pre dip like EPI E Prep 258
Larger parts well be longer, maybe more 2-5分钟
Thank you for this great video. Just gave it a go and the bolts came out like new. Now back to the sandblasting cabinet to do the other 399 bits. Any idea what to soak them in after the parkerizing? Somebody told me that when WD40 is evaporating, it actually attracts water (???). Maybe some kind of gun oil? Thanks again, great information!
WD40 Is ok I have had no problems with it.
go to caswel a company that sells plating chemicals and all the supplies, they have a clear coating to use over zink or phosphate coatings to protect them.
@@charleswittmer2477 Look up Boeshield T-9. All the concourse guys use it. Manufactured by Boeing and used by NASA and many, many others.
What would cause the solution to turn out more of a yellow like beer? Is this actually ok? I wanted to ask first before I tried a sample part. Just incase it was something simple. I followed everything exactly.
I'd like to know the same thing please.
Excellent. I appreciate the detail you put into your instructional videos. I've been using cold bluing to get a similar appearance, but the manganese phosphate appears darker--more of what I am looking to achieve. Definitely going to give your method a try. One question: since you have a zinc plating setup, have you tried the Black Chromate process? Curious how that would compare in appearance and corrosion inhibiting. Keep the videos coming!
Hi Cory
I received a sample of the Black Chromate from my chemical supplier about 1 year ago. I think they send me stuff to try because they consider me a Lab type plating operation. It was a good product. I just don't have a customer base for it. I like to try to reproduce the factory finishes. I hate painted fasteners. On car restoration all your fasteners should be plated or Phosphate coated in Manganese or Zinc. I hope this video helps guys doing there own project to be able to do this in there garage. I am working on a Zinc Phosphate home brew. You can buy this chemical form Palmetto Enterprises. It very good. I think about $55.00 with shipping to make a gallon.Thanks for the input.
Harold
@@backnine Can u tell me please how to make cold zinc phosphating chemicals?
Is this a concentrate or as is? If you get this message please let me know. I am going to be parkerizing some parts tomorrow. I followed your recipe and it looks great. Thank you sir.
I used atomized iron. The same weight of 1/3 of a steel wool biscuit. My parts are looking extremely dark, but as soon as I rinse them off, the black coating comes off and reveals a very light gray (lighter than zinc phosphating). Any clue what could be causing this? I figured the powdered iron would work just fine. I’ve seen it used in other recipes.
Can u tell me please how to make cold zinc phosphating chemicals?
@@Indiansports421 I don’t believe you can make a cold zinc phosphate. The reaction requires heat.
@@smokiesleather we are using cold phosphating chemicals don't required heat,lots of chemicals & company available in India for cold phosphating.
I've attempted to use the recipe and procedure twice, and have failed twice. First time, final concentrate looked like beer, -yellow. seconds time it's kind of purple.
I think I'm using too much manganese. Is it two (2) teaspoons manganese, or 1/2 teaspoon? In video you use 1/2, at what point did you add the remaining manganese?
It could be I'm having difficulty maintaining temp, as my current thermometer sucks...
Get a candy thermometer at Walley World. Too much Manganese Dioxide will not hurt. You will leave it in the bottom of pan when you filter it off. You can use a full biscuit of steel wool. Has to dissolve completely. Let it cool and settle over night. Filter in a gallon jug and top off with distilled water. It should be a light green color and clear. As you use it you will get evaporation so you have to keep adding distilled water to keep level up as you are using it. let me know if it works out.
This reminds me of my mommies' recipe. She would make it for us kids sometimes on Sundays after church during the summer of love.
Is it the clean-n-etch from lowes? Could you put up a picture of the product please
Yes
When You say You use only distilled water, because of the minerals and salts in tap water - do You think de-ionized water would be good enough?
Thamks for another interesting and good tutorial video! ;)
Deionized water is more purified than Distilled H2O. More purity == more $$$. Yes, it would work, but is it worth the extra cost? Depends on your application and quality goals, yes?
Did you ever do your gun?
Your black oxide video of "metal parts" is no longer on CZcams is that still available via private link? I bookmarked that because how good the information was.
Gun parts
CZcams doesn't like that.
@@backnine. I have searched and searched and searched for the last six months and while I have read many articles, nothing is as information packed as your videos for the DIY'er.
Could you post a link to the video on something like Google Drive or Dropbox and post the link here or PM me with the link? Do you have any other videos that were taken down? There are several books on the subject like Angier, R.H. (1936). Firearm Blueing and Browning but they are not as good as your video.
I've downloaded everything I could find that was still up on 5/23/24 but like I said your videos are excellent. A picture or video is worth a 1000 words. Please consider one of the options above or can you try re-posting. Thank you SO much
MnO2 dissolves in H3PO4 painfully SLOW. What you are depositing on those parts is iron phosphate and very little is any at all manganese phosphate. You either have to use KMnO as an oxidiser to increase dissolution of MnO2 or you need to add Mn in some other form like metal Mn or Mn-carbonate. You can also add some form of nitrate to sequester hydrogen and accelerate deposition rate. Adding too much nitrate will have an adverse effect. Target ph should be around 2.75 and free acid to total acid ratio somewhere between 6 and 10.
Hi would KMnO4 help in the disolving of ths MnO2 and in what Quantities
Uhh, uh, uhh, uh, uh, uh, uh. $10 via PayPal for the first person to tell me how many times he said "uhh"...
@@FantomZap 732,918. Do I win? I didn't really notice until I read your comment lol.
I was surprised to see how much Mn was remaining, undissolved...it did look very much like the small teaspoon wasn't consumed...good suggestions for improving the consumption of Mn.
Hi Harold
I am have grave difficulties with getting the solution to work, I have available 98% Phosphoric Acid i have tried to dilute the acid to 50% but i just can't get the solution to look or work like yours does.
For some reason my solution is all brown once finished cooking, the acid is clear too start with.
The cooking pot has a ton of scum around the top which i notice yours does not.
Please help.
Plz send me black zinc pasivtion racpe or camical name send me my watsap no plz help me sir
+923337647158
ما هيه المكونات التي وضعتها
How would you prepare machined parts that have coolant on them before parkerizing. I manufacture lots of specialty small parts that we now pay big dollars for black oxide finish. We really want to set up this up to save black oxide cost, shipping cost both ways and faster delivery time to our customers. Any help would be appreciated. We have discussed using this process many times.
You can clean the parts with mineral spirits to remove oil. Then bead blast the parts with a 140-170 mesh glass bead. This beat blast is very fine and will not effect tolerance. then use process in the video. If you want to use Black oxide room temp go to EPI web site. They sell instablack 333. Very good product. I have a video on the black oxide doing a gun.
what concentrate is phosphoric acid? Home Depot and Lowe's sell "Phosphoric Acid Cleaner" locally. Is this the stuff you use?
I think it was Prep and Etch at Home Depot. It is probably 40%.
i got phosphoric acid with 80%. does that mean i use half the volume of the cleaner you used?
Yes
Blasting with 80 grit garnet or aluminum oxide makes a nice finish
Is this coating food safe? I would like to do some of my knives if so.
I guess no problem
What's cooking chef!!
So I think your cz .380 didn't took manganese coating well like these plain carbon steel parts.
What is the material of the container you made this solution in?
Stainless steel.
@@DarkMatterX1 Thanks for your reply. We actually parkerised tools at my father's unit with your procedure.
Great video. I followed your recipe but I got a grey finish instead of black. Not a real big deal but wondering what you think could be the reason i got a grey finish instead of black.
It depends on the metal. Metal that is hard or heat treated will be more of a gray color.
Thank you for the quick response. It was a heat treated piece. Still covers though and looks good. Thank you again. I looked at other guys recipes on here and yours was the best I found. Appreciate the time you put in to making the video.
When I went in the army in 1976 they issued me a depot new old M15E4 or M16E4 I forget which. That pup was OLD likely an early experimental or trial model from the early 60s. When I got it it liked like new cermacoat. My 45 Colt was the same. Those puppy’s were so rough they would scuff your knuckles but smear some oil on and it was IN There. Beautiful weapons and both a nice light to mid gray. That stuff was TOUGH too. I never saw that parkerized finish on any of my issued weapons again, they were all black.
At 17.28 the author makes the comment that "The solution seems to work better the 2nd time around.", could this because it is lacking in iron? Maybe more steel wool should be added initially.
My guess is that he is over diluting the solution with Distilled H2O. Maybe get faster results with a more concentration from the start 🤔
Strange way to make shake and bake? Lol
So your mix once topped off with distilled water in a gallon jug is ready to use? No need to mix with more distilled water when filling the parking tank? I have a project that wasting a few bucks to make this could save me alot of $$. I was told to wrap a steel wool pad in a coffee filter and submerge it in the tank for at least a half an hour to activate the solution. This might cure the poor covering problem you have on initial parts. Thanks for sharing.
You could put more steel wool in the initial mix it will not hurt any thing. As I said for the car restoration stuff it works great and cheap. You have to keep adding distilled water when you are heating it to keep the level up as you get a lot of evaporation at that temp. I just did a AK47 to try the solution. Most of it came out jet black but the forged parts came light. The guys that sell the park solution have a predip that suppose to solve that problem. You will see that on some fasteners on car parts also. I am trying to find a predip formula and if it works out I will do a add on video. When you are done just filter it put it back in a jug and top off with distilled water and keep using it. It last a long time. You can buy the the pro stuff but the Hazmat fees are killers. Post your results.
I've had AR15 barrels that look lighter like that. I cheat and rub them down with black moly grease and heat them up with a propane torch, then wipe off the excess. good protectant and darkens it too.
I knew the different metal would be a problem on the gun. The receiver on the AK I plug welded the rails and the park took light on the weld circles (not bad) but you can see it. Also I spot hardened the FCG holes and some other high stress areas and they came out about a shade darker. I will paint this one with duracoat to even it out. The Park will be a good primer + when you park it it gets into all the areas paint won't get. I am starting another AK and bought a fully hardened 80% receiver and will spot weld the rails. I may buy the the predip and try some parts with the home brew and post a result. What makes the park bite good is to media blast the parts. I use a 100-400 mesh glass bead it real fine.
@@backnine Sandblasting is a key issue here. Also, make sure after sandblasting you never touch the part again until you are finished. After sandblasting soak the parts in brake cleaner or acetone for 20 minutes. But never touch the part again until you are done... meaning if your last step is parkerizing then remove your part from the tank (with gloves on) then oil it up. Then you can touch it with bare hands. If your last step is a tactical coating then do not touch the part with bare hands until you have painted the part and it has been cured... oven or whatever.
I saw another video where the guy had a purchased kit of chemicals that included a pre-dip. He said the pre-dip smelled like muriatic acid. Muriatic acid might etch the surface of the part and make it more receptive to the manganese phosphate
Your finishes come out splotchy because you are touching the pre-finished parts with your bare hands. You are getting skin oil on the surface so the manganese is not adhering evenly. Use your gloves for all steps, and your finishes will be more uniform. Thanks for sharing!
I find I get the best finish adhesion by washing the parts to be coated in soapy water, rinse and dry, and give them a microetch in muriatic acid for 30 seconds to a minute, re-rinsing, and finally submerging in solution by a thin wire hanger.
What have you got against prepositions, guy?