How to protect steel from corrosion?

By galvanising or by applying anti corrossive paint

Galvanize, paint,epoxy coating

By coating (galvanization, painting,..), cathodic protection, sacrificial anode , etc. It depends on environment 

1. Application of zinc coating – steel galvanization it’s a process which creates a coating of zinc over metals surface.

2. Application of paint coating – painting creates coating barrier to moisture (which also beautifies metal structures).

Surface preparation:1. Painting type (with using coting system to avoid the corrosion.2. Hot dip Galvanizing.

addition of chromium to steel increase its corrosion  resistance.

If you wish to protect steel structures from corrosion, you need to consider the following:

If the metal does not present corrosion, apply an anticorrosion agent, epoxy or special primer to the structure before applying final coat of finish paint. If metal will be exposed to extreme sea mist and/or sea crystals, then a special marine paint or epoxy must be apply as finishing paint according to the manufacturer's instructions.

If the metal presents signs of corrosion in a small amounts, you need to apply a sandblasting bath to remove all corrosion,  sand off any extra corrosion not removed by sandblasting and apply anticorrosion primer or epoxy, before applying finished coat of marine paint.

If metal presents corrosion to the point of loosing 1/3 its size or more, it must be replaced and not repaired. Trying to repair the structure at this point will present a hazzard situation and will put in danger the  strength and resistence of the steel.

1-Corrosive Layer by the designer according to the construction code (may be4-8mm)

2-Galvanized Layer

3-sacrifice anodes (cathodic protection)

4-paintings(epoxy especially) with sand blasting

                       first of all you cant protect steel from corrosion

Any protection method that would protect surface of steel from oxidinsing:

1) Painting / coating.

2) Cathodic protection.

Prevent uniform attack corrosion by protecting the metal surface. Uniform attack corrosion (sometimes shortened to "uniform" corrosion) is a type of corrosion that occurs, appropriately, in a uniform fashion over an exposed metal surface. In this type of corrosion, the entire surface of the metal is under attack from corrosion and, thus, the corrosion proceeds at a uniform rate. For example, if an unprotected iron roof is regularly exposed to rain, the entire roof surface will come into contact with roughly the same amount of water and thus will corrode at a uniform rate. The easiest way to protect against uniform attack corrosion is usually to put a protective barrier between the metal and the corroding agents.This can be a wide variety of things - paint, an oil sealant, or an electrochemical solution like a galvanized zinc coating.