Wheel Corrosion: Causes, Prevention and Treatment

Corrosion is the silent enemy of alloy wheels. Unlike dramatic pothole damage or obvious curb rash, corrosion develops gradually, often going unnoticed until significant damage has occurred. Understanding what causes wheel corrosion, how to prevent it, and what to do when it develops protects your investment and maintains your vehicle's appearance.

This guide covers everything you need to know about wheel corrosion, from the chemistry behind it to practical prevention and treatment strategies. For comprehensive wheel maintenance guidance, see our ultimate wheel care guide.

Understanding Wheel Corrosion

Corrosion isn't simply "rust"—it's a complex chemical process that affects aluminium alloys differently than steel.

How Aluminium Corrodes

Aluminium alloys don't rust in the traditional sense. Instead, they undergo oxidation when exposed to oxygen and moisture. This process creates aluminium oxide, which appears as a white, powdery substance on affected surfaces.

Unlike iron rust, which continues spreading aggressively, aluminium oxide actually forms a protective layer that slows further corrosion. However, this natural protection is imperfect, and under certain conditions, corrosion continues beneath the oxide layer.

Galvanic Corrosion

Alloy wheels can experience galvanic corrosion when different metals contact each other in the presence of an electrolyte (like salt water). This electrochemical reaction accelerates corrosion at the junction between metals.

Common galvanic corrosion scenarios include:

• Steel wheel weights on aluminium wheels
• Steel lug nuts without proper coatings
• Contact with steel brake components

Pitting Corrosion

Pitting creates small holes or cavities in the wheel surface. This localised corrosion often begins at finish defects or areas where protective coatings have failed. Pits can penetrate deeply into the alloy, causing structural weakening in severe cases.

Filiform Corrosion

This distinctive corrosion type appears as thread-like tracks beneath clear coats and paint. It typically starts at finish damage and spreads outward in worm-like patterns. Filiform corrosion is particularly common on wheels with compromised clear coats.

Causes of Wheel Corrosion

Understanding what triggers corrosion helps you prevent it.

Finish Damage

The most common corrosion cause is damage to protective finishes. Chips, scratches, and cracks in paint, powder coating, or clear coat expose bare aluminium to the elements.

Common Finish Damage Sources:

• Curb rash and kerb contact
• Stone chips from road debris
• Harsh wheel cleaners
• Automatic car wash brushes
• Brake dust etching

Once the finish is compromised, moisture and contaminants reach the bare metal, initiating corrosion.

Environmental Factors

Cape Town's coastal environment presents particular corrosion challenges:

Salt Air: Coastal areas expose vehicles to salt-laden air that accelerates corrosion. Salt acts as an electrolyte, speeding electrochemical reactions.

Humidity: High humidity provides the moisture necessary for corrosion reactions. Cape Town's winter rains create extended periods of elevated humidity.

Road Treatments: While less common in Cape Town than colder climates, road treatments and de-icing chemicals in other regions are highly corrosive.

Chemical Exposure

Various chemicals accelerate wheel corrosion:

Brake Dust: Hot brake dust is chemically active and corrosive. Left on wheel surfaces, it etches into finishes and promotes corrosion.

Harsh Cleaners: Acidic or highly alkaline wheel cleaners can damage protective finishes, creating entry points for corrosion.

Tyre Dressings: Some tyre dressings contain chemicals that damage wheel finishes when they contact the wheel surface.

Manufacturing Defects

Occasionally, corrosion results from manufacturing issues:

Inadequate Preparation: If wheel surfaces weren't properly prepared before finishing, coatings may not adhere correctly, leading to premature failure.

Thin Coatings: Insufficient coating thickness provides inadequate protection, allowing corrosion to develop sooner than expected.

Porous Castings: Some cast wheels contain microscopic porosity that allows moisture penetration despite intact surface finishes.

Recognising Corrosion

Early detection allows intervention before corrosion becomes severe.

Early Warning Signs

White Powdery Deposits: The most obvious sign of aluminium corrosion. White, chalky deposits indicate active oxidation.

Bubbling Under Finish: Bubbles or blisters in paint or clear coat often indicate corrosion developing beneath the surface.

Discolouration: Unusual colour changes, particularly darkening or yellowing, may indicate corrosion beginning.

Rough Texture: Previously smooth surfaces becoming rough or pitted suggests corrosion development.

Advanced Corrosion Signs

Flaking Finish: When corrosion advances, finishes begin flaking away, exposing corroded metal beneath.

Deep Pitting: Visible pits in the metal surface indicate significant corrosion that has penetrated beyond surface oxidation.

Structural Concerns: In severe cases, corrosion can weaken wheel structure, though this is rare with proper attention.

Prevention Strategies

Preventing corrosion is far easier and less expensive than treating it.

Maintain Protective Finishes

Your wheel's finish is its primary corrosion defence:

Address Damage Promptly: When chips, scratches, or other finish damage occurs, address it quickly. Touch-up products provide temporary protection until professional repair is possible.

Avoid Harsh Chemicals: Use pH-neutral wheel cleaners designed for alloy wheels. Avoid acidic or highly alkaline products that can damage finishes.

Careful Cleaning: Use soft brushes and microfibre cloths. Avoid abrasive tools that can scratch protective coatings.

Regular Cleaning

Consistent cleaning removes corrosive contaminants before they cause damage:

Weekly Cleaning: Regular cleaning removes brake dust, road salt, and other corrosive substances. See our guide on how to clean alloy wheels for proper technique.

Thorough Drying: After cleaning, dry wheels completely. Standing water, especially in crevices, promotes corrosion.

Post-Exposure Cleaning: After exposure to salt spray, road treatments, or other corrosive substances, clean wheels promptly.

Protective Treatments

Additional protection supplements your wheel's factory finish:

Wheel Sealants: Synthetic sealants create a protective barrier over your finish, providing additional defence against contaminants.

Ceramic Coatings: Professional ceramic coatings offer superior, long-lasting protection. They're particularly valuable for wheels in harsh environments.

Wax: Traditional wax provides basic protection, though it requires frequent reapplication due to brake heat.

Environmental Considerations

Minimise corrosive exposure where possible:

Covered Parking: When available, covered parking reduces exposure to salt air and moisture.

Prompt Washing: After coastal driving or exposure to road treatments, wash your vehicle including wheels promptly.

Winter Wheel Sets: In areas with road salt, consider dedicated winter wheels to protect your primary set.

Treatment Options

When corrosion develops, various treatment approaches exist depending on severity.

Minor Surface Corrosion

Light surface oxidation can often be addressed without professional help:

Cleaning: Thorough cleaning with appropriate products removes surface oxidation and contaminants.

Polishing: Light polishing with appropriate compounds can remove minor surface corrosion from certain finish types.

Sealing: After cleaning and polishing, apply sealant to protect the treated area.

Moderate Corrosion

More significant corrosion typically requires professional attention:

Spot Repair: Localised corrosion can sometimes be treated with spot repairs, addressing affected areas without refinishing the entire wheel.

Clear Coat Repair: When corrosion is beneath clear coat, professional removal and reapplication of clear coat may be necessary.

Severe Corrosion

Extensive corrosion requires comprehensive treatment:

Complete Refinishing: Severely corroded wheels need complete stripping and refinishing. This removes all corrosion and applies fresh protective coatings.

Structural Assessment: Before refinishing severely corroded wheels, professional assessment ensures structural integrity remains adequate.

Replacement Consideration: In extreme cases, corrosion damage may be too extensive for economical repair, making replacement the better option.

Professional Treatment Process

Understanding professional corrosion treatment helps you appreciate its value.

Assessment

Professionals evaluate corrosion extent, finish type, and wheel condition to determine appropriate treatment.

Stripping

Affected finishes are removed through chemical stripping, media blasting, or mechanical methods, exposing bare metal.

Corrosion Removal

All corrosion is removed from the bare metal surface. This may involve chemical treatment, mechanical removal, or both.

Surface Preparation

The clean metal surface is prepared for new finish application, ensuring proper adhesion.

Refinishing

New protective finish—whether powder coating, paint, or other treatment—is applied according to proper procedures.

Quality Control

Finished wheels are inspected to ensure complete corrosion removal and proper finish application.

Conclusion

Wheel corrosion is preventable with proper care and attention. Maintaining protective finishes, cleaning regularly, and addressing damage promptly keeps corrosion at bay. When corrosion does develop, early intervention prevents minor issues from becoming major problems.

Your wheels' appearance and longevity depend on protecting them from corrosion. The effort invested in prevention pays dividends through preserved appearance, maintained value, and avoided repair costs.

For corrosion treatment and wheel refinishing services, contact Speedline Mags. We serve Cape Town's Northern Suburbs including Bellville, Brackenfell, Durbanville, Parow, and Kuilsrivier, providing expert corrosion repair and prevention services.