45 auto & 30 carbine


#1

I have a 45 Auto with the h/s of W.R.A. 45 AUTO & 30 Carbine with a h/s of LC 56 both of them have steel cases. Both cases are a dark gray/black color. What is the coating or plating on these?
Carolyn


#2

The finish on the carbine case is one of a family of chromate protective finishes. When the case was new it wasn’t dark but rather a shiny yellowish-silver “mother of pearl” effect which has darkened over the years. The wikipedia has a whole bunch on chromate finishes that may help. I’m not familiar with the WRA case. Jack


#3

I have considerable experience in the application of chromate conversion coatings (basically a solution of chromic acid) to aluminum prior to painting, but none involving steel. Chromating of bare steel does not work well, as steel generally must be phosphated (Parkerized) or galvanized prior to chromating. I’d describe a chromated surface as being more of a yellow-gold hue, but that’s subjective.

It would be interesting to know exactly what process was used to chromate steel cartridge cases. My guess is that the cases were galvanized first. Or maybe the steel alloy used for cases might take chromating without pretreatment.


#4

Here is a direct quote from the book “Record of Army Ordnance Research and Development, Volume 2 Small Arms and Small Arms Ammunition, Book 2 Small Arms Ammunition”, Office of the Chief of Ordnance, Research and Development Service, Washington, DC (Jan 1946), Chapter 15 - Steel Cartridge Cases, on page 255 in the general introduction to the chapter:

“Protective finishes for steel cartridge cases were extensively investigated. The most satisfactory coating, phenol-formaldehyde resin lacquer, was unsatisfactory from the point of view of application to mass production methods for small-arms ammunition. The finish adopted was commercially known as Zinc-Cronak, and consisted of zinc plating followed by dipping in chromic acid solution.” (my emphasis added here). Note that this is a 1946 publication.

There is more detailed information about the various steel case finishes trialed in the section that discusses the .50 cal Ball Cartridge.

The chapter is 16 pages long and has a good refernce section at the end. I can scan the chapter and if anyone would like a copy please email me. The scan would be a pdf and it would probably end up being quite large though. I do not know if this is a common book or not. I picked it up in an aution a little while ago.

Hope this is useful. regards.


#5

Both of these cases look like they were Parkerized as they are not bright in color and the color is very uniform over the whole case
Carolyn


#6

The zinc plating (essentially galvanizing) prior to chromating would make sense. What many may not be aware of is that Parkerized (phosphate) finishes on steel gun parts require a chromate rinse to impart maximum corrosion resistance. followed by oiling. A phosphate finish alone is not very corrosion resistant.

I have no idea whether phosphating of steel cartridge cases followed by chromating was practiced much as a production metal finishing operation, but, if so, it probably would have been effective. Depending upon the phosphating chemicals used, the resulting coating color would range from gray to black. Phosphating also provides a superior base, or primer, for application of sprayed-on firearms Teflon finishes. Beretta’s “Bruniton” pistol finish is allegedly a polymer coating (possibly Teflon) over a Parkerized surface.

I notice the previous discussion on the 100 round box of FN 7.62X51 mentions a phosphate coating for steel cases: “Cartridge cases are made by the German “Bonderisation” (Phosphated steel) process.”