Hmmm... that's weird. I've never seen it on any of my ropes, probably have run many 1000's of feet through Dan House style sleeves. Then again I don't own any white ropes. I've seen discoloration from friction hitch burn/wear, it happens over time no matter how slow you go.
Rust? That's very strange. I guess none of sleeves ever get rusty. I use them in the rain but they still don't get rusty. I guess I dry them out well enough after.
Looks like white rope shows it. Home Depot conduit has a poor minimum bend radius, makes it difficult to keep it on the branch when you're installing it.
ErieBuoy posted this conduit spec
a while back, it's the best I've used, a good balance of durability and flexibility.
Thanks for the tip, I haven't had much problem installing my sleeves but I don't have anything else to which I can compare them. Once these sleeves are worn out/lost/given away I'll probably order some of the other stuff.
I have seen the black ghost shadowing on ropes from some conduits. In my fantasy world I sent the blacken rope down to the NCIS lab where Abby was able to perform a Mass Spectrometer analysis which she determined by ion cyclotron resonance the black substance is indeed zinc oxide. But really I just guessed.
Critical thinking leads me to surmise that any moisture transferred off the rope or airborne humidity will react with some of the galvanize plating in select conduits. Over time the inner walls will darken and the longer unused the more the reaction. Upon use, the rope rubs the oxide off onto the rope and the lighter the color the greater the contrast.
If you are seeing red stains then your should discard the offending sleeve since you have abraded off all of the zinc coating and now are rubbing on the bare steel metal. Since longer rope life and clean ropes are both great benefits of using rope sleeves I suggest you replace them; preferably with the original new and improved official size and weight endorsed by Super Bowl Hall of Famerâ€™s Dan House Rope Sleeves. Now available personally autographed by the inventor. I know it is a shameless product plug but hey the more people protecting the cambium layer the better I like it.
I was checking on some advises and forum regarding best rope that I can use on tree swings for adults. Planning to purchase on at https://treeswingstore.com/adult-tree-swings/ and also planning to have DIY.