Moisture inside bottle cage mounts, how do I prevent rust??
 

Just got my first real bike, a Trek fx2, that I'm loving! It came with a pre-installed Kryptonite lock attached to the bottle cage mounts, and today, after riding in some light rain I decided I wanted to attach it to a different set of mounts. I was able to change it with no problem, but thinking back this evening, I didn't do anything to dry off the bike before I switched the mounts... I remember that the screws seemed to be wet with what I assumed to be grease on them, but worst case scenario I just screwed a nice grease/water mixture into my cage mounts :)

Maybe I'm overreacting, but if all I want to do is remove moisture from the mounts am I fine just going in with a dry Qtip and regreassing the screws? Just looking for the easiest solution to something that may or may not even be a real issue. Thanks!

I have seen Sailboat equipment where Antisieze Compound, Marine Grease, and even bars of Gulf Wax smashed into screw and bolt holes to prevent salt water seepage.

Al frame, Al cage, stainless screws

Where I always apply silver antiseize:

Pedals.
I don't need to heat them up with a MAPP torch for removal when I use my Park Tool PW-4.

Freewheel to hub threads.
They are easier to clean without getting gasoline seeping into the mechanism. I also replace the dork disc, buyers like things that look new.

Seatposts.
I tell buyers I charge $100 to remove stuck seats posts.

All M5 frame screws.
The silver antiseize is really way less work than dremel grinding slots into screws or welding nuts to headless tops.

The usual way to insure water is gone from threads is to wipe them off and let them evaporate off any remaining moisture. Using a water displacer (as in WD40) to further rinse/flow moisture off the threads is another idea. Q tips can leave the cotton fibers behind but that shouldn't be a problem.

What is a problem with many current bottle mounts is how they are installed and what they are made of. These days most all Al (and carbon, more later)( frames use what's called a Rivnut. They are essentially hollow and internally threaded rivets that are placed in the frame's hole and then compressed on their self, just like a pop rivet.

One problem this method can bring is that sometimes the threaded portion of the rivnut is deformed and can cause the bolt to not easily thread in, or out. The rivnut can become uncompressed enough to spin within the frame's hole. This is worsened by thin wall tubing and by tubing that is not embossable by the AL rivnut, the rivnut doesn't get a good enough "bite" into the tube and in time can loosen.

Any corrosion or grit inside that rivnut will increase the friction between the bolt and the rivnut. This increases the need for that rivnut to be really tightly installed, lacking this the rivnut can spin in the frame. While there are stainless steel rivnuts most all I see are AL. Which can corrode on it's own over time and exposure. Corrosion is of greater volume then the base AL is and will bind up even SS bolts. If non SS bolts are used then galvanic corrosion becomes a greater issue (especially if you carry fluids with salts in them and they drip off the bottle and onto the cage/bolts, or if you ride in wet and salted conditions.

The usual method to address all this is to use a water phobic coating on the bolts, like an oil, some grease or anti seize. The far less usual method is to remove the bolts periodically and clean off the threads in the rivnuts as well as on the bolts.

Carbon frames often use an epoxy as well as the compressing action to secure rivnuts in place. These rarely come loose IME. The absolute worst application of rivnuts are on steel frames due to the even thinner walled tubes. The steel tubes won't allow the softer rivnut to get a good bite also, independent on how thick the tube wall is. Andy

Steel fastener in aluminium frame will likely cause galvanic corrosion over time, particularly if it gets salty from road salt or sweat or spilled electrolyte replacement beverage, so it's a good idea to use a dielectric grease to prevent moisture ingress and reduce chance of seizing. I often use copper loaded grease on my stuff, technically that's a bad idea from an electrolytic point of view - it does seem to help prevent galling, which stainless is prone to suffer. If you replace your (presumably) stainless screws with anodised aluminium fasteners you'll eliminate galvanic corrosion, but they're more inclined to be damaged by a hex wrench - Torx heads are better for this, still use grease.

Sometimes the easiest way is the best.

Put the bike in a warm place, ie. in the sun or near a radiator, and leave a vent hole---- leave a WB screw off.

Any moisture will evaporate and vent.

Greased screw threads don't rust. Don't overthink this.

spray some boeshield or WD40 in there beforehand ?

and grease or anti seize on the bolt threads

/markp

Knew a guy over in Texas City Texas. He lived right next to the sea water and the refineries. His trick was to spray his entire bicycle down with WD40 and then wipe it clean after a long ride. His idea was that it helped protect from the salt water and a bunch of other stuff commonly found in the Texas City air. Do note that the air is much better in Texas City then it was 40 years ago...

https://cimg7.ibsrv.net/gimg/bikefor...d412c09c3.jpeg
wikapedia

I lived in Santa Cruz for a few months (a long time ago) and had a chromed Fuji (Finest). My commute was only just over a mile but went down nearly 200+ feet to almost sea level and up nearly the same amount. Even with frequent wiping off the moist sea air caused rust to start on every tiny scratch, nick and unprotected steel surface. My bike was nearly as happy to move on from there as I was:) Andy