[MASCOM GLOBAL] Corrosion of plastics refers to the deterioration, degradation, or loss of performance of plastic materials caused by chemicals, heat, UV radiation, moisture, oxygen, and other environmental factors. Unlike metals, plastics do not normally corrode by forming rust. Instead, polymer materials may experience chemical degradation, oxidation, hydrolysis, swelling, cracking, embrittlement, or loss of mechanical strength.

This phenomenon is particularly important for plastic products used in chemical processing, construction, automotive components, electrical applications, outdoor products, packaging, pipes, tanks, and industrial equipment. 

Selecting the appropriate polymer, additives, processing conditions, and filler system is essential for improving the durability and chemical resistance of plastic products.

1. What Is Corrosion of Plastics?

Corrosion of plastics is a general term used to describe the deterioration of plastic materials when they are exposed to aggressive environmental conditions. 

During service, polymers may interact with: 

  • Acids and alkalis. 
  • Organic solvents. 
  • Oils and fuels. 
  • Oxidizing chemicals. 
  • Water and moisture. 
  • Ozone. 
  • UV radiation. 
  • High temperatures. 
  • Oxygen. 
  • Mechanical stress. 

Depending on the type of polymer and the exposure conditions, degradation may occur slowly over several years or rapidly under severe conditions. 

Common signs include discoloration, loss of gloss, embrittlement, surface cracking, swelling, softening, deformation, reduced tensile strength, and reduced impact resistance.

2. Do Plastics Really Corrode Like Metals?

Plastics and metals have very different structures, so their corrosion mechanisms are also different. Metals commonly undergo electrochemical corrosion or oxidation, which can result in the formation of rust or metal oxides.

"Corrosion of plastics", on the other hand, generally undergo polymer degradation caused by chemical reactions, oxidation, chain scission, hydrolysis, solvent absorption, or environmental exposure. For this reason, technical discussions often use terms such as plastic degradation, polymer degradation, chemical degradation, environmental stress cracking, and chemical resistance rather than corrosion. However, the term "corrosion of plastics" is still widely used when discussing the resistance of plastic materials to aggressive chemicals and operating environments.

Understanding the corrosion of plastics is crucial when selecting suitable polymers for severe industrial applications, such as chemical processing plants, underground piping, and marine structures.

Unlike metals that lose weight during oxidation, the corrosion of plastics often manifests as swelling, softening, embrittlement, or loss of mechanical strength due to fluid absorption or polymer chain cleavage. Furthermore, preventing the corrosion of plastics requires evaluating factors like chemical concentration, continuous operating temperatures, UV radiation, and mechanical stress levels. By thoroughly analyzing the mechanisms behind the corrosion of plastics, materials engineers can accurately predict service life, optimize design safety factors, and ensure long-term structural integrity.

Ultimately, mastering the principles governing the corrosion of plastics helps prevent catastrophic equipment failures, while continuous research into the corrosion of plastics drives the development of next-generation chemical-resistant polymers.

3. Main Causes of Corrosion of Plastics

3.1. Chemical Exposure 

Chemical exposure is one of the most important causes of plastic degradation. 

Strong acids, strong alkalis, organic solvents, oxidizing agents, oils, and fuels can interact with polymer materials and cause changes in their structure or physical properties. 

The severity of chemical attack depends on several factors, including: 

  • Type of chemical. 
  • Chemical concentration. 
  • Temperature. 
  • Exposure time. 
  • Pressure. 
  • Polymer type. 
  • Mechanical stress. 

For example, a plastic material may show good chemical resistance to a particular substance at room temperature but deteriorate more rapidly when the temperature increases. 

3.2. UV Radiation and Sunlight 

Corrosion of Plastics

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Plastic products used outdoors are continuously exposed to ultraviolet radiation. 

UV exposure can initiate photo-oxidation reactions in polymers, resulting in: 

  • Color fading. 
  • Surface cracking. 
  • Embrittlement. 
  • Loss of tensile strength. 
  • Reduced impact resistance. 
  • Loss of surface appearance. 

For outdoor plastic applications, manufacturers may use UV stabilizers, UV absorbers, or carbon black, depending on the polymer and application requirements. 

3.3. High Temperature 

High temperatures can accelerate oxidation and other degradation mechanisms in polymers. 

When a plastic product operates continuously above its recommended temperature range, it may lose mechanical properties, deform, become brittle, or undergo chemical degradation. 

High temperatures can also accelerate reactions between the polymer and chemicals, making chemical attack more severe. 

Therefore, the maximum continuous operating temperature should always be considered when selecting a plastic material for industrial applications. 

3.4. Moisture and Water 

Water does not affect every polymer in the same way. 

Some polymers can absorb significant amounts of moisture. Under high temperature and humid conditions, certain polymers may undergo hydrolysis, which can reduce molecular weight and mechanical performance. 

For moisture-sensitive polymers, proper drying before processing and appropriate storage conditions are important for maintaining material quality.

4. Common Signs of "Corrosion of Plastics"

Corrosion of Plastics

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Plastic degradation can be identified through several visible or mechanical changes, including: 

  • Surface cracking. 
  • Increased brittleness. 
  • Discoloration or fading. 
  • Loss of surface gloss. 
  • White marks or surface defects. 
  • Swelling. 
  • Softening. 
  • Permanent deformation. 
  • Reduced tensile strength. 
  • Reduced impact resistance. 
  • Environmental stress cracking. 

In some cases, the plastic product may maintain its original appearance while its internal mechanical properties have already deteriorated. Therefore, visual inspection alone may not always be sufficient. 

For critical industrial applications, mechanical testing and chemical resistance testing should be considered.

5. How to Prevent and Control Corrosion of Plastics

5.1. Select the Appropriate Polymer 

Material selection is one of the most important methods for preventing plastic degradation. 

Different polymers have different levels of chemical, thermal, and environmental resistance. The polymer should therefore be selected based on the actual service conditions. 

Important factors include: 

  • Chemical type. 
  • Chemical concentration. 
  • Operating temperature. 
  • Exposure time. 
  • Pressure. 
  • Outdoor or indoor conditions. 
  • Mechanical requirements. 
  • Required service life. 

Choosing the correct polymer during the design stage is generally more effective than trying to correct material degradation after the product has already been manufactured. 

5.2. Use Antioxidants 

Antioxidants can help reduce oxidation during plastic processing and service. 

They are particularly useful in polymers exposed to elevated temperatures, oxygen, or long-term thermal stress. A properly designed antioxidant system can improve thermal stability and help maintain polymer properties over time. 

However, the appropriate antioxidant type and dosage depend on the polymer, processing conditions, and application. 

5.3. Use UV Stabilizers 

For outdoor plastic products, UV stabilization is an important method for reducing degradation caused by sunlight. 

UV stabilizers and UV absorbers can help slow down photo-oxidation and maintain the appearance and mechanical properties of the polymer for a longer period. 

The selection of a UV stabilization system should be based on the polymer type, expected UV exposure, product color, operating environment, and required service life. 

5.4. Control Processing Temperature 

Plastic degradation can begin during the manufacturing process itself. 

Excessive processing temperature, long residence time, excessive shear, or improper processing conditions can cause thermal degradation of polymers. 

Manufacturers should carefully control: 

  • Barrel temperature. 
  • Mold temperature. 
  • Screw speed. 
  • Residence time. 
  • Processing pressure. 
  • Cooling conditions. 
  • Drying conditions. 

Optimizing these parameters helps minimize polymer degradation during manufacturing and improves the consistency of the finished product. 

5.5. Control Material Moisture 

For moisture-sensitive polymers, proper drying is essential before processing. 

Excessive moisture can cause hydrolysis during processing, resulting in molecular weight reduction and loss of mechanical properties. 

Manufacturers should therefore follow the recommended drying temperature and drying time for each polymer grade and maintain proper storage conditions to prevent moisture absorption.

6. The Role of Calcium Carbonate in Plastic Materials

Calcium carbonate (CaCO₃) is one of the most widely used mineral fillers in the plastics industry. It can help reduce raw material costs, increase stiffness, improve dimensional stability, and modify selected properties of plastic products. 

However, calcium carbonate should be selected and used according to the specific polymer and application. Important factors include CaCO₃ purity, particle size, particle size distribution, moisture content, surface treatment, and dispersion performance. 

For plastic products requiring high chemical resistance or long-term performance in aggressive environments, calcium carbonate should be considered as part of the overall material formulation, rather than evaluated separately from the polymer and other additives. 

The compatibility between the filler, polymer matrix, additives, and processing conditions can have a significant effect on the final performance of the product.

7. How to Improve the Service Life of Plastic Products

To achieve better long-term performance, manufacturers should consider the entire material system rather than relying on a single solution. 

A suitable approach may include: 

  • Selecting a polymer with appropriate chemical and thermal resistance. 
  • Evaluating the actual operating environment. 
  • Selecting suitable antioxidants and UV stabilizers. 
  • Controlling moisture and raw material storage. 
  • Optimizing processing temperature and residence time. 
  • Selecting compatible fillers and additives. 
  • Conducting chemical resistance and mechanical testing. 
  • Monitoring product performance during actual service. 

This systematic approach can help reduce premature failure and improve the reliability of plastic products. 

Conclusion 

Corrosion of plastics is different from the traditional corrosion of metals. In plastic materials, it generally refers to polymer degradation caused by chemicals, heat, UV radiation, oxygen, moisture, mechanical stress, and other environmental factors. 

The main signs of degradation include cracking, embrittlement, discoloration, swelling, deformation, and loss of mechanical properties. 

To prevent and control corrosion of plastics, manufacturers should select the appropriate polymer, understand the operating environment, optimize processing conditions, control moisture, and use suitable additives such as antioxidants and UV stabilizers. 

For industrial plastic applications, evaluating chemical resistance and environmental durability during the material selection and product design stages is essential. Proper formulation and processing can help extend product service life, reduce maintenance costs, and improve the long-term reliability of plastic products.