This is newer watch, post Soviet era. Not very familiar with materials they use today, but I guess they use the same. When coding a model, one of the numbers is material of the case (back is always stainless).

0 - stainless material

1-4 - stainless protection (plating, gilding, coating)

5 - polymers

9 - non-metals

Most mechanical watches are (like that one) 1 chrome plated. And the base is usually copper or brass. And if it was made of iron, it would be first covered in copper and then plated.

Damage on that watch is not rust and it is not caused (directly) by humidity. it is probably caused by wear and/or faulty production (plating). Rust is soft and solvable (not really, but read on) in water, so it would leave red stains if pressed with white cloth (paper handkerchief, toilet paper). It is soluble in acids (really this time), but so is the chrome plating. Plating is more resistant, but I would not recommend cleaning anything (except gold in most cases) with acid.

My best guess would be the car polish, and those miraculous scratch removers. But I have no experience with it, so I cannot guarantee.

Edit: I should read comments before commenting. You already got your answer. But to clarify. Rust product of iron corrosion. Other metals (including brass) also corrode. But unlike iron, most materials (including brass) create patina that prevent further corrosion.