Uhhmm........Satin Nickel, Hard Chrome and NP-3 are all surface platings. Whether done by electrode activation or electroless, they all add material to the surface of the metal. If done correctly, platings will wear very well but they are all thicker than before being plated.
Parkerizing and bluing are surface conversions. A chemical reaction between the chemicals in the bath and the metal causes a change in the surface of the metal.
Aside from the physical and chemical differences between the two types of finishing, the biggest difference are the changes in dimensions. Any type of plating process will increase the parts overall size. No, it's not much but it can cause difficulties in precision fitted parts. I have taken parts that fit to loose and tightened them up by plating them. A surface conversion finish will add nothing measurable. (By me at least!!) In fact, a surface conversion finish process that's done incorrectly can remove metal. It's an acid!
Parkerizing get's it's durabilty because it tends to soak up oil. The surface can feel dry but the oil is down inside the "pores" protecting the metal. Many finishers will use that soaking effect to soak up whatever spray type finish they're using. It gives a better bond and wears better.
Some spray on finishes are an absolute BAD THING for the internal workings of a firearm. One of the very common ones is Polane under a different name. It's made for dump trucks and is way to thick for close tolerance moving parts. Even worse, it will not burnish so it just "balls up" as it's worn.
"To thick" is not necessarily a bad thing...as long as the finish will burnish. Burnishing means that the parts wear against each other evenly. The high points or to thick part wears off but the low points remain as is. The overall effect is that the parts start out a little snug but then wear to a perfect match with a noticeable decrease in friction, especially if the finish contains a lubricant.
The worst thing about any "spray and bake" finish is that it looks so easy. It's not difficult if you have the correct equipment and the knowledge to use it. Sand blasting the parts with dirt scraped up from the back yard, spraying it on with a two dollar air brush after the metal was heated with a hair dryer and then curing it in the kitchen oven while cooking a pizza at the same time will NOT result in a durable good looking finish!
The bottom line is that there are many different firearm finishes available. What's right for you for one firearm may not be right for somebody else or a different firearm. Working guns are different from competition guns which are different from go-to-the-range guns, etc. etc. Some will rust if not baby'd, some will shine in the dark, some aren't as pretty as the other one, some look dangerous just sitting there, etc. The trick to picking the correct finish for your gun, is to ask the right questions. Do you want discreet, glow in the dark, rust proof, works slick, show only, etc.??????? Ok ok! That was a few bottom lines. Keep yer powder dry, Mac.
Tuff-Gun Finishes. The Name Says It All.
Mac's Shootin' Irons
http://www.shootiniron.com
