Rust prevention

1. Galvanization

• Galvanization consists of coating metal with a thin layer of another such metal. Typically, zinc is applied by either hot-dip galvanizing or electroplating.
• Zinc is traditionally used because it is cheap, easy to refine and adheres well to steel. In more corrosive environments (such as at sea) cadmium may be used.

• In these cases the coating provides cathodic protection to metal,where it acts as a galvanic anode rusting in preference.

• More modern coatings add aluminium to the coating as zinc-alume, aluminium will migrate to cover scratches and thus provide protection for longer. These rely on the aluminium and zinc oxides protecting the once-scratched surface rather than oxidizing as a sacrificial anode

2. sacrificial anode

• Cathodic protection makes the iron a cathode in a battery formed whenever water contacts the iron and also a sacrificial anode made from something with a more negative electrode potential, commonly zinc or magnesium. The electrode itself doesn't react in water, but only provides electrons to prevent the iron rusting.

3. coating

• Corrosion control can be done using a coating to isolate the metal from the environment, such as paint

4. Passivation

• Given the right conditions,a thin film of corrosion products can form on a metal's surface spontaneously, acting as a barrier to further oxidation.
• When this layer stops growingat less than a micrometer thick under the conditions that a material will be used in, the phenomenon is known as passivation
• Passivation in air and water at moderate pH is seen insuch materials as aluminium,stainless steel, titanium,and silicon.