Protecting bare metal (steel)

[excossack]

If I have a bit of metal that I have cleaned back to shiny bare metal, but want to paint it and still see the bare metal what can I use?
Clear Varnish, lacquer, clear stone chip?
In this case I have made the chassis number more visible by removing the paint covering it.

 

[Chipper]

If it must be bare, clear 2k clear over well degreased metal will last a good while. Or linseed oil, or Gibbs Brand, been using that though it takes forever to dry and it's not cheap.
Or thin coat of etch primer, thin colour coat. Unless the numbers are faint, if there's not too much paint ir should be OK.