Lexus GX 2010+ :: Driver Side Door Making Squeaking Sound - Rusting Hinge Bolts

Due to the rain this weekend I decided to clean out my interior and do some maintenance. Lately my driver-side door has been making a squeaking sound. As such, I decided to lube up all the doors just in case. Upon inspecting all the doors/hinges I found that both the driver-side rear door and passenger-side rear door hinge bolts are rusted real bad. These are the bolts that connect the hinge to the door rather than the hinge to the door frame.

I inspected the door for any sign of water intrusion, but could not see anything out of ordinary. Also, nothing else was rusted or appeared to be water damaged. I inspected all the other hinge bolts around the car for comparison and they were fine. It is strange that both rear passenger doors have this issue. I bought the vehicle used and the Carfax comes back clean with no accidents or damage reported.

The only other time I have seen this is when the door has been worked on, and a socket was used which stripped the protective paint off the bolt. Even then only the rough edges of the bolt rusted, and not the entire thing. While I could foresee one door being worked on, I do find it strange that both would have needed work. However, this assumption does not rule out the possibility.

My only other issue of concern which may play into this is the surprising amount of sand I find on the exterior. As good as one can clean a car there are always some places that will never get fully clean. With that said, while the exterior is clean I have found sand residue in little crevices (weep holes) and corners throughout. I am sure that sand and moisture would play a part in causing rust to accumulate, except that no other parts show any sign of rust. This is certainly bizarre to me. I plan on replacing the bolts, but would like to remedy the problem before hand if possible.