Testing Powder Coat Adhesion Myths

[reddog81]

I’ve seen a number of posts where it’s mentioned that you should take extra special precautions when handling bullets to be powder coated. I’ve seen people state that you shouldn’t rinse the bullets with water because it’ll leave a film that prevents adhesion, don’t touch the bullets because the oils from your hand will mess up the process, don’t drop onto a cloth towel because somehow it’ll prevent adhesion of the PC, rinse bullets with acetone before PC’ing to ensure they are ready to take the PC, etc.

I’m no expert but I’ve PC’d 10,000 bullets and never ran into any of the above problems so I wanted to do a torture test to see what you could actually do before the PC process without any adverse effects. I had a pile of ugly bullets – bullets from the first casting of a new mold while the mold was warming up. These bullets have wrinkles, but the base appears to be fine and should shoot good enough for short 9mm ranges.

For the torture test I covered the bullets in saliva, rolled them in a pile of drywall dust, rolled them in a pile of crud underneath my reloading bench that included spilled gun powder, dog fur, dead bugs, and anything else that has accumulated over the months since I last cleaned. These results are pictured below. I let this dry for a day and then proceeded to PC the bullets. Before PC’ing I rolled the bullets in my bare hands to get rid of any of the large debris and also help test the theory that oil from your hands will prevent PC adhesion. I coated the bullets in one of the reds offered by Smoke4320. The bullets were baked for 20 minutes at 400 degrees. The oven was not pre-warmed. The bullets passed the smash test as pictured. One of the bullets was hit with a hammer and flattened and the other was hit once then rotated 90 degrees and hit again resulting in a cube shape. There is no sign of the PC flaking or coming loose. I tried to remove the PC from various bullets with my fingernail but nothing happened. I’m guessing these will shoot just fine. I made up a magazines worth for the test and I’m now debating on which gun to shoot them in - Glock 17 or CZ 75B.

My normal process obviously doesn’t include any of this and I’m not sure what this will prove other than that many of the often repeated anecdotes around PC and bullets don’t really hold water when put to the test. These bullets only need the PC to remain in place for one trip down a couple inches of a gun barrel. If I was PC’ing a motorcycle part or even lawn furniture that has to withstand years of abuse it would be a different story For bullets I think the most important part of the process is baking at the correct temp for the correct time.

[fredj338]

Yeah like you I haven't seen an issue just taking bullets out of the cardboard box I store them in, coat & bake. No I don't wear gloves or do anything special to the bullets.

[Walks]

I water drop into a clean bucket of water every time, I spread the bullets out to dry in the sun on the same bath towel, can't remember the last time I washed it. Up end bucket to dry on edge of patio concrete, next to colander that separates bullets from water.
Store bullets in clean plastic jugs. Dump PC'ed bullets into old cardboard 500rd bullet boxes.

Never had a problem PC'ing. But then I don't take any special care either.

[Eddie17]

You stuck the boolits in your ��?

[Eddie17]

Just joking! I’ve never had a problem with Powder Coat adheasion on my boolits!

[reddog81]

You stuck the boolits in your ��?

LOL! Not quite... I wasn't sure how to describe spitting on them. I figured if some people have trouble with water this should definitely cause a problem.

[stubshaft]

The only concession I make is to wear gloves. Other than that, no BB's just shake and bake...

[Walks]

Used GRN BB's to start, they wore after a couple thousand bullets. Switched to black BB's, going strong @4,000 44-240grs.

I use rubber gloves to pick out bullets from the powder/BB' combo.

[reddog81]

After reading a thread the other day where a couple of members were arguing over the best way to rinse containments from bullets I decided to test some of the ideas being thrown out. First it mentioned to rinse the bullets with water. This was derided since tap water can contain impurities and salt from a water softener which will supposedly cause chaos with the PC process. Next was suggested to use bottled water and finally it was suggested to use acetone. All this seemed absurd to me so I figured I try worst case scenario and see what happens.

I took 40 124 grain SWC 9mm bullets from a recent casting sessions as sample. I don't have a water softener so I grabbed a spoonful of ice cream salt and some pink sea salt. I mixed the bullets, salt and Des Moines Water Works tap water together, stirred it up and let sit for a few minutes. I then fished out the bullets and let them dry over night. I didn't wipe the bullets down or rinse then off - just threw them in with PC and BB's, shaked and then baked at 400 for 20 minutes. They passed the smash test with flying colors. Even got out the framing hammer for the waffle effect. I haven't shot them yet, but I'm about 99.9% certain there will be no issues.

[Loudy13]

I have also coated 10,000 plus boolits and I did have a problem with adhesion for about a week, not sure I ever did figure out what the problem was but I was able to scratch the powder coating off with my fingernail randomly on a batch of about 400-500 bullets. I did start to wash my water bucket (quenching bucket) thinking maybe it was oil build up in the water. Haven't had an issue since but cant say with confidence that was the actual problem.

I have also shaken boolits and put them on trays for a few days until I have time to bake them and that doesn't seem to make a difference either as far as adhesion they are fine.

Just my 2 cents

[Petander]

Interesting tests.

Here's my most contaminated alloy:



It casts bright,pretty bullets. You can't see anything wrong.

It won't coat properly for 2000 fps 45-70 loads unless I soak freshly cast bullets in 30% HCL overnight. My steel bright bullets turn grey in that time. Rinsed and dried they are dark and dull. And they coat real life great.

I can cast, coat and smash this alloy without soaking,bullets look and smash just fine. And it shoots almost okay with pistols. That "almost" made me look for contaminants. Fired bullets lost some of the coating, sometimes a little leading etc...

So many folks say "My alloy is clean,no contaminants" without even a basic XRF analysis or acid test. Every alloy also reacts differently with added contaminants. And with air. My main contaminant here is Niobium from monotype.

I want the best bullet I can get. You don't need visible dirt to contaminate metals,miniscule amounts of whatever minerals or other metals will do.

[reddog81]

So many folks say "My alloy is clean,no contaminants" without even a basic XRF analysis or acid test. Every alloy also reacts differently with added contaminants. And with air. My main contaminant here is Niobium from monotype.

Contaminants in the lead is something I hadn't considered, nor would I have much knowledge on. I've had up to 5% copper come back from XRF tests sent to BNE years ago, but don't regularly get my alloys tested. Most recent sample was from an alloy mainly comprised of wheel weights and small amounts of linotype.

What does 30% HCL do? A quick google search indicates it might dissolve the Tin and Nb but I'm not sure.

[bmortell]

mainly makes me wonder how useful a bullet smash test is. feel like something has to be Majorly wrong to actually fail

[reddog81]

mainly makes me wonder how useful a bullet smash test is. feel like something has to be Majorly wrong to actually fail

I think most problems are a result of insufficient curing/baking.

Some people have problems getting the powder to adhere to the lead and I think most of those problems are due to people not using the correct supplies. The process is VERY simple if you have the correct container, correct BB's and the right powder. If you're using the wrong supplies it's just a crap shoot whether or not it'll work.

[dverna]

Interesting work RD81

[slide]

This is kinda off subject but I have seen it posted that gunpowder will not affect properly cured powder coat. I will guarentee my powder coat is properly cured. It is affected by some powders and not others. Most of the offenders are pistol powders(double base) What is strange is that two pistol powders, one of them probably at the top as being a powder that is really popular doesn't affect powder coat at all. You will start seeing affects at around three weeks. Rifle powders don't seem to have any affect at all.

[bmortell]

I think most problems are a result of insufficient curing/baking.

ya but ive tested that by cooking for like 2 minutes until as soon as powder melted liquid and it passed smash test just as good as anything else. i think there would have to be something physical preventing the powder from touching the lead to make it fail the test. or the 2 materials are incompatible in some way

[reddog81]

ya but ive tested that by cooking for like 2 minutes until as soon as powder melted liquid and it passed smash test just as good as anything else. i think there would have to be something physical preventing the powder from touching the lead to make it fail the test. or the 2 materials are incompatible in some way

I’m not sure what to tell you. I just follow the 20 minutes at 400 degrees and it works 100% of the time. It’s pretty simple.

[Winger Ed.]

I've often wondered if some folk's problems with adhesion isn't surface contamination,
but not doing the process and curing/cooking properly, and/or using a coating that isn't up to the job in the first place.

I'm not a powder coater, but with paint- I've seen similar problems.
I've found some that stick like poop on a baby blanket, or hang on like a cat on a screen door;
and others that won't hardly stick in a shag carpet if you didn't follow their instructions to the letter.

[popper]

I've PCd bullets that I used OneShot case lube and BLL on prior to PC. NO problem, they shoot fine. Looked like crud but did fine. 145gr PB ~1800 in BO. I do have very conductive skin and found holding the #5 bowel with gloves or heavy towel does help. I use black ASBB and found after a while they get smaller so some of the plastic is wearing off.