The cannon pictured above is a 10" Parrot rifle that burst due to a premature bust of a shell in the bore. The muzzle was chiseled smooth, and it continued in use for 370 more rounds. As the gun was built, used and destroyed during the Civil War, no smokeless powder was involved. The burst tube was cast iron, and the reinforcing band at the breech was welded from a bar of wrought iron, shrunk on. I guess the band could be considered a form of Damascus!

With regard to corrosive primers, I have been doing some internet research this morning, and based on what I have found, mercury fulminate primers were not corrosive. Mercury fulminate primers were discontinued due to short shelf life, which led to misfires and hang fires. Potassium chlorate which replaced the mercuric primers is highly corrosive, but more stable, which is why it was used by the military through WWII.
The true corrosiveness of chlorate primers was not realized until after the advent of smokeless powder. Black powder produces large quantities of unburned residue which absorbed much of the oxidizing residue of the primers, and removal of the black powder residue with water also removed most or all of the chlorate residue, depending on the thoroughness of the cleaning.
Smokeless powder did not leave the quantity of unburned residue of black powder, so a few passes with a brush left an apparently clean barrel, except that the chlorate residue imbedded in the pores of the metal could not be seen.Before the true cause of the corrosion was discovered, it was usually blamed on the smokeless powder. The military found that the corrosion could be avoided by thorough cleaning with soap and water. My early rifle training was at Ft. Jackson and FT. Bragg with the M1 rifle and WWII ammo. On days when we fired, GI trash cans with immersion heaters were set up in the company street and filled with boiling soapy water to clean the rifles.

That is really interesting, Tom, thanks for sharing. Also note that Elemental potassium reacts with water (i.e. humidity) to form a base, Potassium Hydroxide. Basic compounds are highly corrosive and reactive to metals, especially steel. The soap would dissolve and neutralize any traces of KOH that could be present.