Any operation using metal mechanical equipment must be aware of rust and the threat it poses.
In the short-term, rust can increase build-up of contaminants, impairing processes, but it can also result in damage to parts requiring expensive maintenance and repair work, along with mechanical downtime.
When components are affected by rust and lose their integrity, they can also represent a serious health hazard. If left unchecked, rust can ruin equipment entirely and consequently see a loss of investment for enterprises.
Fortunately, there are several options available to prevent rust. Here, we’ll take an in-depth look at rust and the multiple ways it can be mitigated.
Rust is a type of iron oxide. It happens when iron combines with oxygen and moisture, causing corrosion.
Visually, rust is an orange-brown discoloration appearing most noticeably on the surface of metal. It can impact iron, but also iron alloys, like steel. Water is the key catalyst for rust.
While metal structures might seem solid to the naked eye, minute water molecules can penetrate the microscopic holes present. This sparks the corrosion process, but where salt is present in the water, corrosion is even faster. Exposure to carbon dioxide and sulphur dioxide also speeds up the process.
Rust makes the metal expand, placing great stress on its structure. Simultaneously, the metal is weakened, becoming brittle. Iron oxide is permeable to both water and air, which means the metal under the rust layer continues to be eaten away.
Below, we examine six ways to prevent rust from taking root.
1. Correct storage
The most obvious way to prevent rust is to keep equipment away from excessive moisture.
Water reacts with iron and air to create rust, so environments with no moisture can effectively prevent rust. However, even standard air contains a percentage of moisture as humidity.
To entirely prevent rust, an air- and water-tight seal would be required, which makes using equipment impossible. However, when equipment is stored or shipped, it can be stored sealed to prevent rust when inactive.
A common method of rust prevention, galvanising is accomplished by electroplating hot-dip galvanising.
The steel or iron parts are coated with a thin protective layer of zinc, which effectively stops water and oxygen from contacting the metal underneath. However, the zinc also creates a sacrificial layer. Zinc is far more reactive than both iron and its alloys, so it oxidises before the iron components.
3. Rust resistant alloys
Using equipment designed to be rust resistant is another option.
All metals corrode over time, but at different rates. Alloys are made of two or more metals, making them more resistant to rusting. In technical terms, all steel types are alloys, as they are made by combining carbon and iron. However, including other metals, like nickel, chromium and manganese, among others, can create various steel alloy types with different benefits.
Some, like stainless steel, are designed to entirely prevent rust. Although they are not completely resistant to corrosion resistant, they rust a lot more slowly. Other alloys, like COR-TEN steel, will get an initial layer of rust, and then cease rusting when conditions are right.
Blueing immerses steel parts in a solution made of potassium nitrate, sodium hydroxide and water, and can offer limited protection against rust for smaller steel items.
The name “blueing” come from the blue-black finish that this approach gives metal.
5. Powder coating
A dry powder is applied evenly to a clean metal surface in powder coating.
Afterwards, the metal is heated, transforming the powder into a thin protective film. Nylon, urethane, acrylic, polyester, epoxy and vinyl powders are all available and applied using electrostatic spraying.
6. Oil based coatings
Perhaps the most cost-effective and flexible way to protect metal against rust is by using an organic coating to form an effective barrier, sealing out corrosive elements.
Oil-based coatings are an excellent solution for preventing the penetration of both oxygen and water. There are wide range of different lubricants, from conventional mineral oil and grease, to specially designed synthetic solutions like rust preventatives, that offer advanced protection.
Oils can flow through mechanical systems, coating all components with a thin but strong film that seals them against air and water. Greases are oil based, but include a thickening agent that gives them increased viscosity and tackiness, so they stay in place for longer, offering an extended defence against rust.
Cutting-edge rust preventatives can deliver even greater protection, however. Rust preventatives can use a petroleum or mineral oil base, but include special additives like rust inhibitors that supply stronger protection against rust. Rust preventatives can come in a grease or oil-based format to suit different aims, like protection during storage or protection during operation.
A built-for-purpose solution, using a rust preventative is a leading way for operations seeking an affordable and effective way to protect their equipment from corrosion.