How to Protect Metal from Corrosion
If you are responsible for machinery on an industrial site, taking steps to prevent corrosion is an essential part of maintaining the performance and longevity of your equipment. Similarly, engineering and metal fabrication companies will need to ensure that their parts and machinery are corrosion-proofed to prevent them from being damaged.
Corrosion can lead to equipment failure, increased maintenance costs, and even safety hazards if left unaddressed.
Fortunately, there are a number of best practice methods that you can employ on site to ensure that any risks of corrosion to your valuable equipment are kept to a minimum.
In this blog post, the experts at Broughton Lubricants will discuss the various methods you can use to protect your metal assets, both in terms of products you can purchase and maintenance steps you can take to reduce the risk.
What is corrosion and why is it harmful?
Corrosion is a natural chemical reaction that occurs when metals react with the environment around them, leading to the gradual degradation of the material. The corrosion converts the reactive metal surface into a more chemically stable - but structurally weaker -oxidised form.
Because materials have varying electrochemical properties, different metals corrode in different ways, depending on the circumstances. For example, ferrous corrosion more commonly known as rust, results from the reaction between iron, oxygen and water, whereas copper and aluminium may tarnish due to a reaction to oxygen in the air.
In addition to degrading the appearance of your equipment, products and supplies, corrosion can weaken the structural integrity of metal components, making them more susceptible to failure. Furthermore, it can cause machinery to operate less efficiently and create safety risks for workers.
As such, preventing corrosion should be considered a priority for any business. By taking a practical approach to maintenance and corrosion prevention, you can avoid the negative impact it can have on your staff, your operations and your clients.
Method 1: Corrosion-resistant metals
One of the simplest ways to prevent corrosion is to use metals that naturally do not experience corrosion. These are materials with a low level of reactivity, or that form a protective oxide layer that prevents further corrosion. Some common examples of metals with corrosion resistance include:
- Stainless steel: This alloy contains chromium, which forms a passive oxide film on the surface, providing excellent resistance to corrosion.
- Aluminium: This metal forms a protective oxide layer that is highly resistant to corrosion.
- Copper alloys: Materials such as brass and bronze exhibit good corrosion resistance due to the formation of a stable patina (a layer of corrosion product that protects the underlying metal).
Because these materials are naturally resistant to metal corrosion, they can reduce the need for additional corrosion prevention methods. However, it is always best to use these methods in tandem, to maximise the longevity of your equipment and also reduce the risk of corrosion affecting your products.
Method 2: Protective coatings
Applying a protective coating to metals can help prevent corrosion by creating a barrier between the surface of the metal and the surrounding environment. Some common protective coatings include:
- Lubricants: Many lubricant products, when applied during the manufacturing process, leave a protective coat on the finished metal, which can help to protect them from corrosion.
- Paints: High-quality industrial paint coatings can effectively protect the metallic surface from corrosion by sealing out moisture and oxygen.
- Powder coating: These powder coatings are made of dry particles - including nylon, urethane, polyester, epoxy and acrylic - that are applied electrostatically and then cured under heat, creating a durable finish that forms a protective layer against corrosion.
- Organic coatings: These coatings, such as rubber or plastic, are applied to the surface of the metal as a liquid and cure to form a tough, flexible barrier.
It is worth bearing in mind that these protective coatings will need to be periodically stripped and reapplied in order to remain effective.
Method 3: Metal plating
Metal plating is another approach to protective coating that involves applying a thin layer of another, more corrosion-resistant metal onto the surface of a metal component in order to prevent corrosion. Commonly used materials include zinc, nickel, chromium and tin coating, all of which offer excellent protection against corrosion.
This can be achieved in a number of ways:
- Electroplating: A thin layer of chromium or nickel is deposited on the substrate metal via an electrolyte bath.
- Hot-dip galvanisation: This method immerses the substrate in a molten bath of the protective metal, forming a protective layer around the substrate metal.
- Electroless plating: A chemical reaction is used to bond the protective metal coating to the primary metal, meaning an electric current is not required.
- Mechanical plating: This simple method uses cold welding to apply a metal powder to the clean metal surface.
An alternative metallic plating-based approach of preventing corrosion involves the use of sacrificial coatings, which involves layering the equipment with a covering of a different type of metal that is more reactive, such as zinc, aluminium or magnesium. The sacrificial coating will react (corrode) first, protecting the less-active metal from degrading.
There are two main methods available for achieving sacrificial coating:
- Galvanising: This is achieved either by hot-dipping the substrate in the more reactive metal, or by electroplating a thin layer on to the metal surface
- Metal or thermal spraying: The sacrificial metal is heated and atomised into fine particles, which are then sprayed onto the surface using a spray gun.
- Anodising: A sacrificial oxide layer is created by submerging the component in an electrolytic bath and applying an electric current.
Method 4: Cathodic protection
Cathodic protection is a technique used to protect metal surfaces from corrosion by turning them into the cathode of an electrochemical cell. Cathodic protection can be achieved through two methods:
- Impressed current: This method involves the use of an external power source to provide a direct current that counteracts the corrosive electrochemical process.
- Sacrificial anodes: Anodic protection involves attaching a more active metal, such as zinc or magnesium, to the surface. Similar to sacrificial coatings, the sacrificial anode corrodes instead of the metal underneath, providing a protective barrier. This method is often used to protect carbon steel storage tanks.
All of these have been shown to be highly effective corrosion prevention methods, although they need to be complemented by proactive maintenance steps to be most effective.
How design changes can help prevent corrosion
Another factor to consider is the role that the design of the product or equipment itself can play in helping to prevent metal corrosion. For example, to prevent crevice corrosion, it is sensible to take steps to eliminate cracks, pits and divots in the metal where water and debris can collect, rather than draining off the surface of the metal.
It is also advisable to eliminate narrow gaps in the design that allow air or fluid to enter and become stagnant. These steps are particularly important to consider for equipment that is operating in an environment where contact with liquid is likely, as the risk of corroded metal is inevitably going to be high in such cases.
The importance of environmental measures and proper maintenance
Investing in corrosion inhibitors and other effective corrosion prevention methods can be very helpful, but this will work best when combined with proactive maintenance and safeguarding of your metals.
Proactive measures to control the environment around your products and machinery can significantly reduce the risk of corrosion, as can suitable protection methods implemented as part of your maintenance routine. Some steps to consider include:
- Minimise exposure to moisture and humidity by keeping machinery dry and well-ventilated.
- Regularly clean and inspect machinery to detect and address early signs of corrosion.
- When storing metal sheets, corrosion can occur as a result of keeping the materials in contact with each other. By storing different metals in between, this can be prevented
- Implement proper drainage systems to prevent standing water around equipment.
You should also remember the key role that lubricants can play in preventing corrosion. Lubrication helps to reduce wear and tear on machinery and metallic components, and also leaves a protective barrier that keeps out external elements, minimising the effect of oxidation and rust.
Protecting your metal assets from corrosion is crucial for ensuring the longevity and efficiency of your machinery. By understanding the causes of corrosion and implementing appropriate prevention methods, you can significantly reduce maintenance costs and the risk of equipment failure.
To find out more about the lubricants you can use to help protect your equipment from corrosion, browse our product range at Broughton Lubricants. Contact us on 03300 555 655 to learn more about our range of industrial and metalworking products, or email us at [email protected].
Get in touch with us today to learn more about how we can help by calling us on 03300 555 655 or using our online enquiry form.
