I never found Pyrodex corroded any worse than black powder. Indeed, Pyrodex IS black powder, with some sort of flame retardant which keeps it from being classed as a low explosive. When the gooberment regulations went into effect in the 70s to keep small shops from stocking BP, it disappeared and Pyrodex came out to replace it on shelves. It worked fine in my revolvers and I still use it because it's the closest sub to BP and gives that sulfur smell.
I thoroughly clean my guns as soon as I'm done shooting and do not find any excessive corrosion. I also squirt 'em down inside and out with WD40 to displace the water I bathed 'em in which helps.
I keep 777 around. It makes my CVA Wolf shoot HARD, some powerful stuff. I've just NOW started using Blackhorn 209. This stuff will NOT go off with anything, but the proper 209 primer and breech plug designed for the stuff. However, folks here told me about the Magspark...
http://www.warrencustomoutdoor.com/mag-spark.html ...which totally changes a sidelock rifle to even fire Blackhorn 209! I haven't yet bought a breech plug for my CVA Wolf or a drill bit to drill out the old one, but I may get around to that. The magspark I had to try. I had a conversion for small rifle primers for the Hawken, but it wouldn't set off BH209. I must say, I'm totally impressed with it. I installed the old small rifle conversion in my cheap CVA Plainsman I bought used off Gunbroker and now it is 100 percent reliable with Pyrodex. This gun is a 1:48 and I bought it so I could shoot patched RB which it does very well. My Hawken has a 1:24 twist and will only shoot heavy Minies or sabots. I shoot full bore sized Minies in it. It really likes the 385 grain Hornady Great Plains and I have a 360 grain Minie ball mold for it, also, from Lee.
I didn't like BH209 at first, stuff takes a blow torch to set off. But, I didn't know about the breech plug thing for it when I tried it in 2010 when I first heard of the stuff. I knew I couldn't shoot it in a sidelock, but with the magspark, I sure can! This stuff is like smokeless as far as fouling. I can sit down and load and load and never have to brush the bore to maintain accuracy. I can leave it a few days before cleaning and I can clean it with standard rifle solvents like Hoppes number 9.
BH209 is quite expensive, though, but it's available at a gun shop near you. I only shoot it in my hawken, but will shoot it in my CVA Wolf eventually when I get the proper breech plug for it.
It ain't like that Magspark conversion is a new idea, either, first came along in the 1860s. Apparently they had problems with ignition, especially in wet weather, even when BP was everywhere.