Acid has nothing to do with it. Healthy skin has a pretty narrow pH range. Sulfur is what attacks silver, and some people's hand oils and perspiration contain more. My skin is hard on silver. In college I let my silver Bach flugelhorn tarnish so much it was all black and purple. I did keep the inside clean. When I noticed pitting on the valve casings I finally polished it. There was no silver left on any of the contact points, and even some of the nickel silver tubing was pitted. The silver plate on my Schilke X4b held up better (I did maintain it to keep it shiny), though there were patches of raw brass where my right thumb rested on the underside of the leadpipe and between the first and second valve spring towers. And I never could polish the pinky ring enough to get it shiny. On the other hand, I've owned my silver Holton Superbone since 1985 and have logged a lot of hours on it in the last 30 years. The silver plate is still nearly perfect, even at contact points. More nickel in the plating solution? Who knows. I have no idea what attacks modern epoxy finishes. I've only seen wear due to friction, and that limited to where my right thumbnail rubs on the first valve casing.