Metal corrosion is one of the most common causes of component failure in industrial environments. What may start as surface rust or slight discolouration can gradually weaken the metal beneath, affecting performance, reducing service life and increasing the risk of failure.
In many cases, corrosion is often far more than just a cosmetic concern. In harsh operating conditions, metal components may be exposed to moisture, chemicals, salt, abrasion or repeated temperature changes, all of which can cause gradual damage to the substrate if the surface is left unprotected.
Industrial coatings help prevent this by creating a barrier between the metal and its surroundings. When the correct coating system is specified and applied properly, it can reduce the risk of corrosion while supporting the long-term performance of the finished product.
Common Causes of Metal Corrosion
Corrosion occurs when a metal reacts with substances in its surrounding environment. The exact cause can vary depending on the metal and the conditions it is exposed to, but most corrosion is linked to one or more of the following factors.
Moisture
Water is one of the main drivers of corrosion. When moisture sits on an unprotected metal surface, it can act as an electrolyte and allow corrosion reactions to take place. This may come from rain, condensation, humidity, washdown processes or regular contact with liquids during use.
Oxygen
Oxygen reacts with many metals and contributes to the oxidation process. In the case of iron and steel, this reaction can lead to rust. Moisture usually accelerates the process, which is why metal exposed to both water and air is at greater risk than metal kept dry.
Salts & Chlorides
Salts and chlorides can make corrosion develop much faster. They increase the conductivity of water on the metal surface, which speeds up the electrochemical reaction. This is why components exposed to sea air, salt spray or de-icing salts need a higher level of protection.
Acids, Alkalis & Industrial Chemicals
Chemical exposure can break down unprotected metal surfaces or attack weaknesses in an existing coating. Acids, alkalis, cleaning agents, process fluids and other aggressive substances can all contribute to corrosion, particularly where contact is frequent or prolonged.
Galvanic Contact Between Dissimilar Metals
Galvanic corrosion can occur when two different metals are in electrical contact with each other in the presence of an electrolyte such as water. One metal becomes more likely to corrode than it would on its own. This is an important consideration where assemblies include mixed metals, fasteners or conductive joints.
The Effects of Corrosion on Metal Components
Corrosion affects metal components in practical, measurable ways. It changes the surface, weakens the material and can interfere with the way a part fits, moves or performs.
Loss of Material Thickness
As corrosion progresses, it can remove metal from the surface of the component. This loss of material may be uneven, which means some areas can become thinner or weaker than others. On load-bearing parts, even a small reduction in section thickness can affect how the component performs under stress, or cause it to fail entirely.
Pitting & Localised Attack
Not all corrosion spreads evenly across a surface. Pitting corrosion creates small, localised cavities in the metal, which can be difficult to detect at first. These pits can act as stress points, making the component more vulnerable to cracking, fatigue or further corrosion.
Surface Roughness & Contamination
Corrosion can make a smooth metal surface rough, flaky or uneven. This can affect components that need to slide, seal, rotate or maintain close contact with another part. In some cases, the surface may also become sharp, jagged or unpleasant to handle, creating a risk for operators or end users. Loose corrosion products may also contaminate nearby surfaces or fluids, depending on the application.
Loss of Dimensional Accuracy
Many industrial components are manufactured to tight tolerances. Corrosion can change the dimensions of a part by removing material, building up surface deposits or distorting the coated surface. This may affect fit, alignment, movement or assembly with other components.
Damage to Appearance & Finish Quality
Corrosion commonly affects the appearance of a finished component. Rust, staining, blistering or flaking can reduce perceived quality and may make a product look poorly maintained, even if the damage has not yet caused functional failure.
Why Industrial Coatings Are Essential for Corrosion Prevention
Industrial coatings can be used to protect metal surfaces from the conditions that cause corrosion. A suitable coating forms a protective barrier over the substrate, helping to stop moisture, oxygen and contaminants from reaching the metal beneath.
This barrier is important wherever components are expected to perform reliably over a long period of time. The correct coating system can improve durability, reduce maintenance requirements and help protect the component from the demands of its working environment.
However, corrosion prevention is not simply a case of applying any coating. The coating system must be suitable for the metal, the application and the conditions the component will face in service. The best result comes from a complete coating system that includes surface preparation, pre-treatment, primer and a final protective finish.
How Industrial Coatings Protect Metal Surfaces
A protective coating works by separating the metal from corrosive elements in its surroundings. By limiting direct contact with moisture, oxygen and aggressive substances, the coating reduces the chance of oxidation, rusting and chemical attack.
Different coating systems provide different performance benefits. Some are designed for strong corrosion resistance in outdoor or marine environments, while others are chosen because they also provide chemical resistance, abrasion resistance or electrical insulation. The most suitable option will depend on both the component and the conditions it needs to withstand.
For example, powder coating is often selected when both protection and appearance are important. It creates a hard protective layer and, when combined with the right pre-treatment, can provide good corrosion resistance for a wide range of metal components.
In harsher environments, a thicker thermoplastic coating may be more suitable. Nylon coating can form a continuous protective layer around the component, helping to shield the substrate from moisture and environmental exposure.
Corrosion Categories & Coating System Selection
When specifying a coating system, it's important to consider the environment in which the component will operate. ISO 12944 classifies environments from C1 to C5 based on their corrosivity:
- C1 (Very Low): Heated indoor environments such as offices, schools and retail spaces.
- C2 (Low): Unheated buildings and rural outdoor areas with low pollution levels.
- C3 (Medium): Urban, industrial and high-humidity environments such as food processing facilities.
- C4 (High): Industrial and coastal areas with higher levels of moisture, pollution or corrosive substances.
- C5 (Very High): Offshore, coastal and aggressive industrial environments with severe corrosion risks.
As the corrosivity category increases, more robust coating systems are typically required, often incorporating enhanced pre-treatments, primers and greater coating thicknesses. Selecting the correct category helps ensure long-term protection and maximise component lifespan.
Types of Industrial Coatings Used to Prevent Corrosion
Several coating processes can help protect metal components against corrosion. The right choice depends on the part design, required finish and service environment.
Powder Coating
Powder coating is a durable, decorative finish that gives metal components a consistent coating thickness. It is applied by electrostatically spraying dry powder onto the component before curing it to form a hard protective layer.
Its main strengths are durability, appearance and versatility. It suits components that need a hard-wearing, professional finish, and can be combined with the right pre-treatment or primer for higher corrosion performance. Typical applications include street furniture, handrails and automotive components.
Electrophoretic Coating/E-Coat
E-coating (electrophoretic coating) is an economical corrosion-resistant finish that is also widely used as a high-performance primer. The component is fully submerged in a coating bath, allowing the finish to cover edges, recesses and hard-to-access areas evenly.
This makes E-coat especially useful for complex components and production volumes where thin, uniform corrosion protection is required at a cost-effective level. It is commonly used for automotive parts such as under-bonnet components, seat frames and brackets.
Thermoplastic Dip Coating
Thermoplastic dip coating creates a thicker, smooth and continuous protective layer around the component. The heated part is dipped into thermoplastic powder, which melts and fuses to the surface.
This coating offers strong resistance to corrosion, chemicals, UV exposure and weathering. It also helps components withstand handling, impact and long-term wear. Typical uses include medical furniture, automotive springs and outdoor street furniture.
Electrostatically Sprayed Thermoplastics
Electrostatically sprayed thermoplastics provide a thermoplastic finish where dip coating is not the most suitable option. The coating is sprayed onto the component and then fused to form a smooth, durable film.
The process offers thicker coverage than traditional powder coating, along with corrosion, abrasion, impact and weathering resistance. It is often used for stadia seating, rainwater gutters and downpipes, lamp posts and street furniture, and roof rack components.
PTFE Coating
PTFE coating is a thin technical coating used where corrosion protection must be combined with low friction, non-stick performance or release properties. It is applied as a specialist coating system to create a controlled, functional surface on the component.
Its strengths include chemical, humidity and temperature resistance, as well as smoother movement between surfaces and more consistent torque values on fasteners. It can help reduce lubrication needs or improve release from the coated surface. Typical uses include industrial fasteners, cookware, mould tools and under-bonnet automotive components.
Bonded Lubricant Coating
Bonded lubricant coatings are solid film lubricants designed to reduce friction and wear between moving or mating parts. The lubricant coating is bonded to the component surface to create a durable dry film.
The coating remains in place under pressure, which makes it useful for heavier, slower-moving loads where abrasion and wear need to be reduced. Typical uses include load-bearing surfaces, gaskets, bearings and drive chains.
Plastisol Coating
Plastisol coating provides a flexible, rubberised protective finish for metal components. It is applied to the component and cured to form a resilient coating around the surface.
Its strengths include corrosion resistance, chemical resistance, insulation, impact resistance and a softer feel. It can also cushion the surface, resist chipping, reduce noise and improve handling. Typical applications include materials handling parts, plating jigs and grab handles.
The Importance of Surface Preparation
Surface preparation and pre-treatment processes are one of the most important stages in corrosion prevention. Even a high-performance coating may fail if it is applied to a poorly prepared surface.
Before coating, the metal may need to be cleaned, degreased, blasted, treated or primed. These steps help the coating bond to the substrate and perform as intended. Any surface contamination left behind can reduce adhesion and ultimately weaken the coating system.
This is why pre-treatment should be considered part of the full coating process rather than an optional extra. The better the preparation, the stronger the protection.
Choosing the Right Coating for the Application
Selecting the right coating depends on how and where the component will be used. A part fitted outdoors will have different requirements from one used inside a controlled factory environment, and a component exposed to chemicals will need a different level of protection from one chosen mainly for appearance.
The type of metal matters too. So does the expected service life, the level of abrasion and the required finish. For some components, a thin decorative powder coating may be suitable, while others may need a thicker thermoplastic coating or a multi-stage coating system to achieve the required level of protection.
The best results come from matching the coating system to the application from the start. With decades of experience and one of the widest coating service ranges under one roof, Plastic Coatings supports customers in selecting coating solutions that make components more durable and fit for purpose.
