I've noticed that on the inner slide of my conn 88Hcl that the nickel plating is starting to pit in some places, anyone know what could be causing this/ways to further prevent it?
Thanks

I believe those inner slides on the Conn's are chromed. If you have pitting then somewhere along the way moisture, oil, or some other product has sat on the slide and created corrosion or lifting of the chrome. Often you can buff this out. I don't think it will work as well as a new slide, but it can work really well. You might want to have a professional buff it because you are going to want to keep the tube as close to perfectly round as possible.

If you have piting on the inner slide you may also have damage on the inner part of the outer slide (another reason to have a professional technician look at it). To prevent further corrosion you need to neutralize whatever is causing the pitting. A restorative cleaning using polishes, dips, and such is called for. And then when you get it back once a week cleaning every week. And slide preparation when you put it away after playing, not before playing.

Example: Empty moisture out of your instrument when you are done playing and then again when you get home. (If practicing at home empty when you stop and again an hour later). Why twice? Because when you dump the water/spit after playing your instrument it is still warm and as it continues to cool more condensation will accumlate and be sitting in the instrument.

When you've been playing for awhile the oil in your valves and the grease/silicone/etc on your slide have been blown and mixed with spit and water. This water is now sitting on your valve(s) and slide. Clean it off now or when you get home. Not only will this help your instrument last longer but it will be ready to play out of the case first thing tomorrow.