The first time I ever saw anything about not using Hoppes (or any copper removing solvent), on nickel or chrome plated guns was in Guns and Ammo magazine some 30 or more years ago. Jeff Cooper used to have a regular section in the magazine where he answered questions about handguns from various readers. One particular letter sent in by a gentleman living somewhere in South America, dealt with this specific issue. Seems he had a blued pistol and a chrome plated pistol that he cleaned with Hoppes No 9 solvent. He then wiped both guns down, and placed them in a felt lined drawer in his gun cabinet. Sometime later he went to look at his pistols, and while the blued gun was fine, he noticed that the chrome plating on his other gun was beginning to flake and peel off. This happened on the slide that was in contact with the felt lining. He wanted to know how this happened.
Cooper responded that he believed that not all of the Hoppes was cleaned off the guns and that whatever remained, probably drained into the felt lining. There it was in contact with the slide of the gun and most likely was the cause of the plating coming off. Since Hoppes is a copper removing solvent, Cooper thought that it found its way into the copper plating underneath the chrome plating, and went to work removing the copper layer like it was designed to do.
So ever since then I have avoided using Hoppes on any of my plated guns and all of them have been absolutely fine, with all of their plated surfaces completely intact. To keep them looking clean and bright, I use Flitz on them once or twice a year, depending on how much they have been used, handled, etc. I have been doing this for more years than I can remember, and so far everything still looks and works just fine.
