Strange problem encountered with PD'd bullets

[dbosman]

Black has carbon black and the other colors are using titanium dioxides.
A quick check shows carbon black to be 2. - 2.9 on the Mohs scale and titanium dioxides to be 3.82 to 5.13 Mohs. <--- subject to change by people who know or find more than I did.

[MUSTANG]

Although it is as clear as mud to me, I found a Data Sheet on MB55 (attached PDF); and the following for MD-68 as used in the Black Powder Coat:

Attachment 90729

MB-68 Product Description

Low-gloss curing agent MB-68(also known as Hardener MB68)is a salt of organic polycaroxilic acid with a cyclic amidine.
1. Characteristics
Appearance: Fine powder(white)
Melting Range: 210~230º C
Purity: ≥ 99.5%
2. Application
Low-gloss curing agent MB-68 for epoxy resins and epoxy polyester hybrid powder coatings is used to achieve coatings with matt surface having excellent mechanical quality and wonderful reappearance.

[Aunegl]

I think somebody is making mountains out of Mohs hills. A little search on Wikipedia: "On the Mohs scale, graphite (a principal constituent of pencil "lead") has a hardness of 1.5; a fingernail, 2.2–2.5; a copper penny, 3.2–3.5; a pocketknife 5.1; a knife blade, 5.5[clarification needed]; window glass plate, 5.5; and a steel nail, 5.5.[9] A streak plate (unglazed porcelain) has a hardness of 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale."

[xacex]

Earlier in the thread there discussion of the MSDS's for Harbor Freight Powder Coat Paints, but an inability to post them to this thread. Attached are MSDS Sheets for White, Red, Yellow, and the infamous Black Harbor Freight Powder Coat Paints.




Click over each of the 4 docs to get pdf's for each of the different colors.

Thanks Mustang!

[xacex]

I think somebody is making mountains out of Mohs hills. A little search on Wikipedia: "On the Mohs scale, graphite (a principal constituent of pencil "lead") has a hardness of 1.5; a fingernail, 2.2–2.5; a copper penny, 3.2–3.5; a pocketknife 5.1; a knife blade, 5.5[clarification needed]; window glass plate, 5.5; and a steel nail, 5.5.[9] A streak plate (unglazed porcelain) has a hardness of 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale."

As a Geologist I can say Mohs hardness is an important scale to judge suitability of materials for their intended use. We do not want to be using materials above a mohs hardness of 7.5-8 in a gun barrel or there will be rapid wear. Materials lower in the scale may also be abrasive to a lower extent. Mohs is just another tool in the tool box to judge a materials suitability. It was useful in Mineralogy, and Petrology, and it is completely applicable for judging material hardness of coating you may be sliding down the pipe. 95% of the materials we use today were a mineral at some point outside of plant,or polymer materials.
When you want to look of a term regarding Geology, or uses for mineral or their properties use this site. http://www.mindat.org/

It is a little more reputable than Wikipedia, and has a ton of information regarding materials we should, or should not be using.

[OuchHot!]

Please note that mohs does not tell the whole story. A material can be very sizeably anisotropic like graphite. In plane (speaking of crystal lattice) it is very soft. Edge wise the lattice is hell on wheels. I wonder if any of these coatings use fumed silica as a bulking agent to keep it on the article during the early stages of heating? Fumed silica can be very bad even though it too is found in lipstick etc.

note. the matting agent is silica based!!!!!!
I thought as much. I have formulated similar materials and used fumed silica to either get them to hang while the curing reaction starts up or to give a nice finish......might look for high gloss formulations. I am no longer a specialist in this field so I could very well be wrong, but........

[xacex]

You may not be a specialist, but you understand the basic principle of Chrystal structure and I assume types of bonding as well as I do. You bring up a great point about planes, and silica is one that can be very bad depending on its form. Not only is Si hard, but you get into the booked minerals like mica's where the bonds are week in one plane, but very strong in the other you will get a hard,abrasive edge no mater how small the pieces are.
I think it is wise to use all of the tools we have for determining what can be used, not just one like Mohs, or Crystallography. There is so much science involved with these aspects as well as Metallurgy tools we can use that this will take a village to break it all down.
Now, I just got some Copper sulfate to try out adding copper to my melt. I have a pot of lead calling me.

[OuchHot!]

I am a materials scientist for a living (sometimes called a chem. eng, depends on which pays less) and have a metallurgy degree but my advanced study is in polymers. I just have not formulated thermosets like these for many years. Silica any way you cut it (sorry) is going to be abrasive. If the particle size is small enough the process is quite slow. Fumed silica used to be expensive but people's republic got in the act and it is used in a lot of places now. xacex mentions mica. I always got a little nervous when people started dusting their boolits with "motormica". I recall as a kid what happened when I used a graphite based grease in a high speed roller bearing.

In the case of graphite and mica, I suspect the sliding of the boolit orients the lattice and sliding (and the low mohs) predominates. There is no such free lunch with silica.

[Beagle333]

So..... um...... is only the black supposed to be a little "scratchy", or are they all not as slippery as they feel?

[Moonman]

Looks like CARBON BLACK is in the HF black powder.

Coming from the TIRE INDUSTRY, I believe CARBON BLACK

is the FINEST as in SMALLEST SIZE "ABRASIVE" that there is. (1/300,000 of an inch in diameter)

[Thundermaker]

So the take away is "don't use HF matte black"?

[Magana559]

So much for the black boolits I wanted!

[xacex]

I wouldn't completely write off H/F black. If it is mildly abrasive we can use it to our advantage shooting cast boolits. Lapping boolits cost good money, and as it stands it looks like we have a great lapping coating for our rifles and pistols so long as the diameter of the boolit it proper.

[Cane_man]

which colors have the silica in them?

I am a materials scientist for a living (sometimes called a chem. eng, depends on which pays less) and have a metallurgy degree but my advanced study is in polymers. I just have not formulated thermosets like these for many years. Silica any way you cut it (sorry) is going to be abrasive. If the particle size is small enough the process is quite slow. Fumed silica used to be expensive but people's republic got in the act and it is used in a lot of places now. xacex mentions mica. I always got a little nervous when people started dusting their boolits with "motormica". I recall as a kid what happened when I used a graphite based grease in a high speed roller bearing.

In the case of graphite and mica, I suspect the sliding of the boolit orients the lattice and sliding (and the low mohs) predominates. There is no such free lunch with silica.

[OuchHot!]

I just did a search on the matting agent and saw the silica. I would assume that a gloss coating might not use the matting agent and therefor be silica free. A lot depends on the type of silica used. Fumed silica can be very fine and amorphous and not near the problem. The issue is that fumed silica versus ground is more expensive and peoples' republic doesn't bother so much with managing the particle size. I would look up the various agents listed in the msds and try to avoid silica until someone else proves it to be harmless. Sorry...there are too many uncertainties. I am just very nervous about the use of silica as a viscosity modifier or matting agent. It might not be the cause of the erosion shown. Again, I haven't done this kinda work in years and I am just spewing my best wag.

[C. Latch]

Just saw this thread. I'm hoping to get a complete PC kit for Christmas next week - including a pound of HF Black.

My .45 needs a bit of lapping, so this isn't too worrisome, but maybe after a couple hundred rounds I'll need to switch colors.

[Cane_man]

i just ordered some high gloss orange, cures at 340F in 15', i'll see how it goes...

[OuchHot!]

I'm thinking that at the end of the day, this PC technology could be a "holy grail" for us in letting us use more alloys over a broader range of velocities. Maybe even getting the lead dust down in indoor ranges and so forth. I think the PC thing just needs fine tuning and it looks like a good group of you are doing just that.

[bruce381]

kinda off subjest BUT moly disilfide a good solid lube turns from a lube to an abrasive at ?/ forgot 700F or so.
perhaps the Ti dioxide does the same and in the barrel oxidizes and hardens as more booolits go down range?

[popper]

Assuming the HF has TiO2, it gets sticky & gooey in the recycle pot so I'd say no - never any PC residue in the bbl. Can't guarantee it but think the OP has a different problem.