Method of preventing rust - Class 7 PDF Download

How to prevent rust

Exposure to outdoor conditions will increase the risk of rust, especially if the climate is rainy or humid. These are the best ways of preventing rust:

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.

Design

Proper planning during the design stage can minimize water penetration and reduce the risk of rust. Cavities and crevices should be avoided. Joints should be welded not bolted. Drainage holes for water should be considered if appropriate. The design should allow air to freely circulate. For large structures, adequate access should be enabled to allow for regular maintenance.

Galvanization

The process of galvanization involves coating the surface with an external layer of metallic zinc. This is accomplished through hot-dip galvanizing or electroplating. The zinc layer prevents corrosive substances from penetrating further into the metal. In addition the zinc acts as a sacrificial anode which means that the damaging oxidation process of rust will be transferred to the zinc layer.

Bluing

Bluing is a useful technique which offers limited protection against rust for small steel items. The term “bluing” comes from the blue-black appearance of the finish when using this technique. Blueing is often used in firearms manufacture to provide a degree of corrosion resistance.  It’s also used in fine clocks and other metal work.

Bluing is accomplished by immersing the steel parts into a solution of potassium nitrate, sodium hydroxide and water.

Organic coating

Organic coatings such as  paint are a cost effective way to protect against rust. Organic coatings form a barrier against corrosive elements. Oil based coatings are ideal for preventing penetration of water and oxygen. Typical organic coatings are 15 to 25 micrometers thick.

Powder coating

A dry powder is evenly applied to a clean surface. Next, the object is heated, turning the powder into a thin film. There are a wide range of powders available including acrylic, polyester, nylon, vinyl, epoxy and urethane.

Powders are commonly applied using an electrostatic spray process. The electrically conductive object is sprayed with a charged, non-conducting powder. The charged particles are attracted the object and cling to its surface. The object is placed in a hot oven which fuses the particles into a continuous film. The film is typically between 25 and 125 micrometers.

Regular maintenance

Regular maintenance is advised to stop rust forming and halt the progress of any rust that occurred. It’s essential to remove any rust that has formed. A razor blade can be used for small areas. Next any surface grime should be removed using warm water and soap. Lastly a rust resistant coating should be applied to the surface.