My new (bought used) bike had corrosion on screws on handlebars, especially the screws holding the armrest for TT style bars.

I replaced those Allen head screws on the bars but the screws holding the arm rests are no easy to source, so I just removed some rust rubbing them with a rust cleaner and lightly oiled them with machine oil and put them back.

Also had aluminum housing of the shift levers corrosion due to sweat from hands (I talk of those shift levers on the tip of TT bars, not briefter shifts on brake handles), also cleaned them to make them decently looking again but I am wondering if I should smear them with some grease to protect them from sweat, since I too do sweat. I try to wipe sweat drops from my chin on my forearms when I ride but something still drops down...

What kind of oil or grease do people use, if any, to smear on the screws and shift lever housing?

Whatever is close at hand when I need to use such.

If you don't have any close at hand, then buy you some of this and use it for most anything you'd grease on your bike....

https://www.parktool.com/en-us/produ...ant-tube-ppl-1

But it's not the only thing. However if you don't normally grease other things that might have more requirements of the grease, then this is fine.

The best option for this issue is rattle can spray paint in the color of your choice.

Oil is fine for the working parts, but will be annoying on parts you need to touch, and is really a problem on lever bodies under the hoods.

Guess I will just put a drop of machine oil on cloth and wipe it on once in a while. That sweat is aggressive, it corrodes even aluminum and my old bike has rusty top tube where sweat fell on it.

Those screws on bar stem are usually machined from titanium but then they shouldn't rust. The old one must not have been titanium as they rusted around and mainly inside the hole where hex wrench is inserted, it removed the black paint, or should they be anodized?

Marine Grease... Any flavor... Dab it on and wipe it off...

You can use traditional rust blueing on the steel fasteners, which looks good and will last well with an occasional drop of light oil. Aluminium parts can be anodised, although it requires more equipment than bluing. Or you can just clean them up and spray with something like RustOleum crystal clear.

When I buy a bike, I usually take it apart, clean it up, and put it back together. I like to replace all of the hardware with titanium. Most of the bolts on a bike are M5 or M6 size, I just have to measure how long they are, then order them on Amazon. Titanium doesn’t rust, and swapping out the steel hardware can save some ounces of weight.

Seriously? I wouldn't rely on those cheap Chinese screws for my safety. I sweat more riding ten miles than I'd save using titanium fasteners. Also, galvanic corrosion.

Absolutely!

I would do fully forged titanium bolts for mission critical areas and any old corroded cables and housing should be replaced along with any bar tape anywhere because you want to inspect every inch of that bar. Sweat can be corrosive as you have seen but having it sit soaked into bar tape can do some damage to bars and is also just gross and cleaning the tape is fine for newer tape you have installed (or had installed by someone) but unknown tape is a no-go.

Basically any used bike you buy should have a full overhaul done to it as you have no idea what was done or not done to it before you got it and the desire to ride right when you get it will quickly be lost when down the road you have problems that turn into bigger ones (Any Harvey Danger fans?) I had to cut out a 7400 Dura Ace French threaded bottom bracket from a bike which hurt so bad I cannot even explain. I bet it was already seized at the time of purchase but I couldn't tell you because I was more excited to ride it right away than actually do it all properly and do an overhaul.

Ti has a fairly low potential for galvanic corrosion. The real danger is self-welding when titanium is pressed against titanium

I was lucky to buy Titanium screws in 2020, when covid has started. You're right, M5 & 6 in two lengths (I think 18 & 20 mm) is good for everything.

I checked sometimes last year and they sold for several times as much, like they were made of gold.
Could have been due to that boat that got stuck in the shipping canal or the covid that hit the Chinese shipping yard. The reason I was checking was that I thought I needed shorter screws for the head that holds the round tube of the bars but it turned out, I could use the longer ones I already had bought previously. Didn't take the bars off till I was packing the bike for shipping to Europe and I figured I should replace those screws then.

I think those old bolts were likely the original ones that came with the bike, not Titanium and had painted heads with something like black lacquer. That's why they would flake the black off and rust inside the holes where you insert Allen hex key.

Normally looked at, it wasn't that bad, but taking a close up pic revealed their sorry state.

I dug into my photo archive and found pics illustrating those corroded screws. They were in a sorry state but you must take into account that these macro shots always make things look worse than they look to your unaided eyes.
To clean the rust corrosion from those shift levers, I used this Rust remover. It worked quite well. Also used it on screws attaching those TT style elbow rest pads. Those have 'countersunk' heads and I couldn't find replacement, not at the time in 2020.




Head bracket before


Head bracket before


New screws on the head bracket



TT Bar Elbow rest screw - Before


These TT Bar Elbow rest screws (countersunk style heads) I wasn't able to find new ones, I cleaned them a bit and now I smear them with a Permatex Synthetic Grease and wipe off excess.



Rear shift lever before.


Front shift lever before.


Rear shift lever rusty bolt after cleaning


Front shift lever rusty bolt after cleaning