Answer the following:
What is done to prevent corrosion of metals?
We can prevent corrosion by selecting the following things:
1. metal type
2. protective coating
3. environmental measures
4. sacrificial coatings
5. design modification
Metal Type :
One simple way to prevent corrosion is to use a corrosion resistant metal such as aluminium or stainless steel. Depending on the application, these metals can be used to reduce the need for additional corrosion protection.
Protective Coatings :
The application of a paint coating is a cost-effective way of preventing corrosion. Paint coatings act as a barrier between metal and atmospheric moisture to avoid its contact. For example : black paint.
Another possibility is applying a powder coating. In this process, a dry powder is applied to the clean metal surface to avoid its contact with surrounding oxygen. For example : acrylic, polyester, epoxy, nylon and urethane.
Environmental Measures :
Corrosion is caused by a chemical reaction between the metal and gases in the surrounding environment. By taking measures to control the environment, these unwanted reactions can be minimized. For example : this would be decrease by treating the water in water boilers with softeners to adjust hardness, alkalinity or oxygen content.
Sacrificial Coatings :
Sacrificial coating involves coating the metal with an additional metal type that is more likely to oxidize.
There are two main techniques for sacrificial coating:
Cathodic Protection : The most common example of cathodic protection is the coating of iron alloy steel with zinc, this process is known as galvanizing. Zinc is a more active metal than steel and when it starts to corrode it oxides which inhibits the corrosion of the steel. This method is known as cathodic protection
Anodic Protection : Anodic protection involves coating the iron alloy steel with a less active metal, such as tin. Tin will not corrode, so the steel will be protected as long as the tin coating is in place. This method is known as anodic protection
Design Modification :
Design modifications can help reduce corrosion and improve the durability of any existing protective anti-corrosive coatings. Ideally, designs should avoid trapping dust and water, encourage movement of air, and avoid open crevices. Ensuring the metal is accessible for regular maintenance will also increase longevity.