I have a very cheap Chinese made scooter and the rust is everywhere even on top of paint and where the paint has scratched off e.g on the side and main stand, if my keeping it dry do you mean wiping it down after rain?
What you describe sounds to me like the manufacturer didn't properly coat the metal, and the finish is porous. The coating on the metal is the only thing that protects it from rust. Rust is aggressive and it's progressive, as the iron in steel is converted to iron oxide, it expands, flakes, pits and greatly weakens. It eventually becomes porous and this exposes more surface area for the rust to eat away. If you want to know more about how rust forms, google "how does rust form". If you want to know more about how to combat it, google "rust repair". You'll find a lot of info. Here's an article that is relatively easy to understand:
How to Repair Minor Rust on a Car
The good news is that the rust you describe sounds like relatively light, surface rust. It is a lot of work, but if I was in your shoes, and wanted to preserve the machine as long as possible, I'd
- Scrape, wire brush, sand or otherwise physically remove the little bumps, removing the soft rust deposits.
- Sand all the existing finish, because it has already proven unable to protect the metal.
- Prime the surfaces with a good rust preventative primer.
- Paint the surfaces with a good quality, rust preventative paint.
POR-15 is a good, but expensive, rust preventative coating:
POR-15 Technical Information
Living in the rust belt and riding my machine year around is why I prefer painted surfaces to chrome. Paint can be fixed, chrome, not so much. Purists will scoff, but I've been known to use a paint brush on my vehicles. With a good quality brush and good technique, one can produce a finish that is certainly not show quality, but does the job. To me, even a crudely painted fender looks better than one that is pocked with rust.
Keeping your machine dry in the environment and usage pattern that you describe is going to be somewhat impossible, but wiping it off will at least reduce the salts in the dirt from contributing to the problem. Once you have removed existing rust and recoated, if you take that path, it will be much easier to prevent it from re-occurring. Don't forget to pay attention to the inside of the mudguards and the nooks and crannies under the seat and so on.