In order to protect the steels, the galvanization process is largelly used (a thin layer of zinc is deposited on steel surface) because of its low cost.  

Chrome or Nickel are also used for protection. 

Please have a look to the standard electrode potential of metals in a basic corrosion book. 

Dear J. Sundaresan,

The best way to protect low carbon steel against corrosion is to use zinc coating or zinc alloy coating such as Zn-Ni, zinc deposit is largelly used in automotive industry, however, the corrosion of materials in water is due to presencce of oxygen, therefore, in the deionized water, if there is the dissolved oxygen, the corrosion could take place, you can find in the literature many papers dealing this topic, best regards

Maixent 

If you could provide more details of your intended application, it would help to give you more direct answers to your question.

I'm guessing that since you specify DI water, there is some desire to keep the water deionized over time even as you desire to protect the steel.  The only realistic way to achieve this is to coat the steel with an appropriate epoxy coating that is properly cured.  Various metal coatings for steel are imperfect in coverage, and some even contribute to ionic build-up over time.  So corrosion might not be your only concern. 

Potable water programs in the US specify such coatings to protect both the substrate and the water in the tank.  The best method of applying the epoxy coating would be by cathodic electrocoat, which is the standard in the automotive and appliance industries for corrosion-resistant primers.  But that application method may be beyond what your environment offers, in which case I suggest 2-pack solventborne epoxy compositions that need to be well-mixed before application by brush, roller, or spray. 

Yes, galvanized or chromium-coated steel plate will rust in deionized water after a prolonged time.

You can enhance corrosion resistance by applying paint top coats. These coatings are easily painted. Paint acts as a barrier, to  protect the underlying  coatings. For example, Zinc is an excellent substrate for paint coatings because if the paint film is broken,, zinc’s high corrosion resistance prevents undercutting of the paint film. Even if the coating damage does reach the steel base, zinc’s cathodic action will prevent the steel from corroding.

I agree with F. Louis Floyd and recommend you contact Enecon - (516) 349-0022 and speak to Michael (Mike) O'Shea [email protected]. If they don't have the solution, they will be able to recommend someone who does. They will need to know your exact purpose to make sure what they recommend is fit for purpose.