Cathodic Protection:

The use of cathodic protection, supplying an external electric current to the iron so in which it acts as a cathode and has no anodic fields, is another method of preventative chemical control. This could be accomplished through the use of an external voltage source or through the use of a sacrificial anode (example for zinc) that will corrode and give the current.

Removing Corrosive Agents:

Chemistry control in the form of removal of corrosive agents from a system is a hugely used method.  One technique is using deaerators to erased dissolved oxygen and to a lesser extent carbon dioxide.  Treating the water through softening and demineralization erased the dissolved solids and decrease the conductivity.