Why does corrosion occur

Filiform corrosion occurs when water breaks through the coating underplated or painted surfaces. This type of corrosion starts at places where there are small flaws in the coating.

It eventually spreads and causes weakness in the structure. Galvanic Corrosion: This type of corrosion happens when two separate metals are placed in a corrosive electrolyte. This creates a galvanic couple between the metals.

One metal now the anode, while the other becomes the cathode. The metal which is the anode now corrodes more quickly than usual, while deterioration slows on the cathode. Environmental Cracking: This type of corrosion is the result of a number of conditions in the environment, such as temperature, chemicals, and stress. There are four kinds of environmental cracking: Stress Corrosion Cracking SCC Corrosion fatigue Hydrogen-induced cracking Liquid metal embrittlement Flow-Assisted Corrosion: This occurs when wind or water dissolves a protective oxide layer on the surface of a metal, and then exposes the metal to deterioration.

Fretting Corrosion: This happens where there is repeated surface motion that can come from vibration. High-Temperature Corrosion This is caused by corrosive compounds formed during combustion, and may also be produced by sulfidation, carbonization, and high-temperature oxidation. Preventing Corrosion There are several techniques that can stop or slow corrosion: Environmental Modification: This is simply changing the environment of the metal to reduce unwanted chemical reactions, such as limiting contact with rain or seawater.

Metal Selection and Surface Conditions: Understanding the causes of corrosion leads to selecting the right type of metal. Monitoring of surface conditions such as cracks and crevices can reduce rates of corrosion.

Cathodic Protection: This is an electrochemical process that protects against galvanic corrosion discussed above. Corrosion Inhibitors: These are chemicals that react with the surface of the metal or the gases in the environment that cause corrosion. Plating: Metallic plating, such as electroplating, can inhibit corrosion and provide an attractive finish to the surface.

Coatings: Paints and other organic coatings can protect metals from the corrosive effects of environmental gases. Take a metal structure such as the Statue of Liberty. It looks strong and permanent. Like nearly all metal objects, however, it can become unstable as it reacts with substances in its environment and deteriorates. Inside the statue, however, corrosion caused serious harm over the years. Some metals acquire a natural passivity, or resistance to corrosion.

This occurs when the metal reacts with, or corrodes in, the oxygen in air. The patina that forms on copper and the weathering of certain sculpture materials are examples of this. The protection fails if the thin film is damaged or destroyed by structural stress — on a bridge, for example — or by scraping or scratching. In such cases the material may repassivate, but if that is not possible, only parts of the object corrode.

Then the damage is often worse because it is concentrated at these sites. Harmful corrosion can be prevented in numerous ways. Electrical currents can produce passive films on metals that do not normally have them. Where the affected iron particles were, has now become a corrosion pit, and where they are now, is called the corrosion product rust. Corrosion can happen at any rate, depending on the environment that the metal is in.

However, since atmospheric corrosion is so widespread, it is recommended to take effective precautionary measures when it comes to corrosion prevention. Depending on the situation and application, you may be able to treat the area that has corroded.

If the affected area is small and treatable, you may require some tools and products to remove it. Begin by removing the rust from the metal using a tools such as a grinding wheel or needle gun. Be careful not to cause any additional damage to the metal. You will also want to take this time to look at the application as a whole for other premature signs of corrosion.

One of the best ways to prevent corrosion is to apply an Anti-Corrosion Protective Coating.