I have been trying out different lubes for a few years now. A different lube for each bike (4)
I started to use T9 on my MTB and was impressed with ease of application, how smooth the chain moved and chain cleaning was a minimum. Well, 2 years later and I wanted to change transmission. The rear derailleur, chain ring and cassette were covered in a very dense film of T9. Very, very difficult to remove. Several hours and I'm still working on it.
Just wanted to tell my experience if you are considering this product

I used Boeshield T-9 Bicycle Lubricant on a 90s-vintage hybrid that I ride exclusively on the road; a bit more than 5000 km in a period of about one year.

It worked well for me, and I did not experience the amount of build-up that you describe. Perhaps we were using it differently.

If you're getting a 'very dense film' of lube you're doing it wrong. T9 is a great lube, you're applying in incorrectly. Too much lube, not enough rag.

The instructions were pretty simple. Apply, let dry and wipe off excess. Maybe in some circles, that's challenging.
All good. Let it go for what it's worth

Longtime T9 user here. I've experienced no such problems, but I attend to my transmission more regularly than biennially.

T-9 bought here in gallon containers, there on various places on 10+ bikes in the household and in other applications, often in combinations with other ingredients, in particular enhancing its staying power. It has been developed for airplanes to stay put and provide corrosion protection. When it comes off, it is a negative in my applications.

Ha ha right? I use Boeshield T-9 regularly and I like it for what it is. It was developed by Boeing as a penetrating protectant. It is supposed to dry leaving a waxy coating behind. Everything I store in long term boxes/bins get sprayed down with it with the understanding that it will need some amount of solvent cleaning to look its best later on down the road. This little snip from their website: "T-9’s unique formulation of solvents and waxes was engineered to penetrate metal crevices deeply, displace moisture, dissolve minor corrosion, and leave a clean, waxy coating with long-lasting durability" https://boeshield.com/about/

As they say, build up and longevity are a feature, not a bug, Boeshield's primary purpose is as a
corrosion preventative, not a lubricant, though it does lube well. A review of the marine literature
where salt water spray is used for months as a test of corrosion inhibition capacity of various
preparations suggests Boeshield stacks up well for longevity.

I’ve used T-9 for 15+ years, many bikes. Never had an issue and drivetrains stay clean. Apply, wait 20 min or so and wipe completely dry. Excellent product for mtb or road bikes.

Not sure if there is difference between T-9 and what is marketed as bicycle specific. T-9 was specified to be used on the joints of an aluminum framed folding kayak I had..... pretty much certain if not used the joints would freeze and it would not fold anymore

???

My bike shop guy recommended it to me many years ago and I’ve been using it ever since, no problem with my chain.

Here’s a problem I have had though, bottom bracket bearings! I live/ride in central Florida’s heat and humidity, and I sweat a lot all summer on a typical 50 mile, 3 hr ride, 5 days a week. How long should a bottom bracket bearing last and is there any way to get some T9 down in there to make it last longer? I seem to go through at least 1 a year (8,000-10,000 miles) sometimes 2 per year. I almost never ride in the rain or on wet roads, but I’m sure some of my sweat is getting in there. Any way to stop that?

I've seen T-9 build up to an impossible to remove sludge before. It is somewhat random when it happens, maybe 1 in 100 bikes. My theory was riders that lube the chain and ride right away, so it ends up all over the place even if they try to wipe the chain with a rag.

I clean my chain with the 3 wheel brush scrubber every 200 miles and then lube it with T9, spin it a few times then put a rag around it and spin it a few more times, no problems with buildup. My problem is trying to lube/clean the bottom bracket. Do I have to pull the crank arm off or can I just squirt a little T9 down there and spin it in?

T9 would not be my choice for any bottom bracket..... if it is cup and cone it needs grease, anything cartridge, outside bearing , really don't need lubrication

What solvent do you use?

One of my daughters in Portland tried T-9 (not Boeshield chain lube) on her chain, I got the buildup off easily with OMS so I suspect any degreaser would work.

Odorless mineral spirits is my first choice because it is cheap when purchased in large cans from the paint thinner section of your local hardware store and can be reused indefinitely to soak small parts in. Just like gunked up grease, the T-9 residue will likely need some scrubbing with an old tooth brush to get it all off. The stinky solvent fumes pretty much rise exponentially when using other paint thinners or de greasers so bear that in mind. Never gasoline.
Edit: If talking frame tubes, I have found that any automotive paste wax will dissolve the T-9 residue with some gentle massage but just watch out for grit on your paint/chrome.

Have you actually examined the bearings? Are you sure the corrosion is the problem?? In any case, the solution to corroding bearings is the ceramic version of those. The ceramic bearings are often ridiculed in the cycling context, but they are a 'put them on and forget it' solution for the corrosion.

Yes, I’ve seen them after my bike shop guy pulls them, and they are nasty! I like the idea of the ceramic bearings, does Trek sell them or do I have to find the right size on my own? Also, are they a lot more expensive than the steel ones? I think I paid $49 for the last bearing.

When bearings are bought from bike part suppliers, they are usually seriously marked up. For the same price you might be able to get ceramic bearings from a supplier for whom the bearings represent the main line of business. I cannot tell you what size you need for your bottom bracket. From my records, I bought Enduro bearings.

How so? The races are steel, the balls are ceramic. The steel can still corrode.

The cartridge ceramic bearings for BB would normally have corrosion resistant races, see here. Enduro also offer SS bearings that are a cheaper option than ceramic. Enduro resellers, also on Ebay, may offer lower prices than the manufacturer.

Thanks for the tip. I ended up using alcohol and it worked out.

Corrosion 'resistant' isn't corrosion proof, just like water resistant isn't water proof. And you don't think stainless steel is corrosion proof do you?