There is a difference to what metals will do exposed to open air versus materials sealed, air-trapped, protective-covered... etc.... etc.

Good gun oils are cheap - average shooter/hunter may use 50 cents of oil per year to properlyprotect a life-long investment-- stuff lasts for 10-15 years in application(s)&is specially formulated for your firearms.

You can purchase the WD-40.... I will pass.