Rust is a form of iron oxide. It occurs when iron combines with the oxygen in the air causing it to corrode. Rust can affect iron and its alloys, including steel. The main catalyst for rust to occur is water. Although iron and steel structures seem solid to the eye, water molecules are able to penetrate microscopic gaps in the metal. This starts the process of corrosion. If salt is present, for example in seawater, the corrosion will be more rapid. Exposure to sulfur dioxide and carbon dioxide will also hasten the corrosive process.
Rust causes the metal to expand, which can place great stress on the structure as a whole. At the same time, the metal will be weakened and become brittle and flaky. Rust is permeable to air and water, so the metal beneath the rust layer will continue to corrode.
How to Prevent Rust?
Exposure to outdoor conditions will increase the risk of rust, especially if the climate is rainy or humid. The best ways to prevent rust include:
Using rust resistant alloys
Design considerations
Galvanization
Bluing
Organic coating
Powder coating
Regular maintenance
Using Rust Resistant Alloys
The most popular rust resistant alloys are stainless steel and weathering steel.
Stainless steel contains a minimum of 11% chromium. This allows the formation of a protective film of chromium oxide which acts as a shield against rust. The protective film will re-form if damaged. Corrosion resistance can be further enhanced with the addition of nickel.
Weathering steel, also known as “COR-TEN” steel, contains up to 21% of alloying elements such as chromium, copper, nickel and phosphorous. The alloys form a protective rust patina which reduces the corrosion rate with time. COR TEN steel tends to be cheaper than stainless steel.
Meghna Thapar 3 years, 10 months ago
Rust is a form of iron oxide. It occurs when iron combines with the oxygen in the air causing it to corrode. Rust can affect iron and its alloys, including steel. The main catalyst for rust to occur is water. Although iron and steel structures seem solid to the eye, water molecules are able to penetrate microscopic gaps in the metal. This starts the process of corrosion. If salt is present, for example in seawater, the corrosion will be more rapid. Exposure to sulfur dioxide and carbon dioxide will also hasten the corrosive process.
Rust causes the metal to expand, which can place great stress on the structure as a whole. At the same time, the metal will be weakened and become brittle and flaky. Rust is permeable to air and water, so the metal beneath the rust layer will continue to corrode.
How to Prevent Rust?
Exposure to outdoor conditions will increase the risk of rust, especially if the climate is rainy or humid. The best ways to prevent rust include:
Using rust resistant alloys
Design considerations
Galvanization
Bluing
Organic coating
Powder coating
Regular maintenance
Using Rust Resistant Alloys
The most popular rust resistant alloys are stainless steel and weathering steel.
Stainless steel contains a minimum of 11% chromium. This allows the formation of a protective film of chromium oxide which acts as a shield against rust. The protective film will re-form if damaged. Corrosion resistance can be further enhanced with the addition of nickel.
Weathering steel, also known as “COR-TEN” steel, contains up to 21% of alloying elements such as chromium, copper, nickel and phosphorous. The alloys form a protective rust patina which reduces the corrosion rate with time. COR TEN steel tends to be cheaper than stainless steel.
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