Corrosive Wear

Corrosive wear is a type of material degradation that results from the combined effects of chemical attack and mechanical action. It typically develops in aggressive environments where protective surfaces break down over time. Here are the main contributing factors:

1. Chemical Exposure: Contact with substances like acids, alkalis, salts, or oxidizers initiates chemical reactions that weaken the material surface.
2. Mechanical Interaction: Erosion, abrasion, or repeated friction removes the compromised outer layer, revealing fresh material to ongoing chemical attack.
3. Environmental Stressors: Extreme temperatures, high humidity, and salt-laden air (as found in marine settings) can significantly accelerate corrosive wear.
4. Material Limitations: Metals or polymers lacking corrosion resistance or mechanical toughness are more likely to degrade quickly under stress.
5. Contamination: Dirt, debris, or embedded particles promote both corrosion and mechanical wear by disrupting surface integrity.
6. Electrochemical Reactions: When dissimilar metals are joined in the presence of an electrolyte, galvanic corrosion may occur — further accelerating wear at contact points.

To prevent corrosive wear, it’s important to use corrosion-resistant materials, apply protective coatings, and manage environmental and mechanical conditions through design and maintenance strategies.

Wear and erosion both cause material loss, but they happen through different mechanisms. Recognizing the difference helps in selecting the right materials and protective strategies for industrial applications.

Wear:

• Definition: Wear is the gradual degradation of a surface due to mechanical contact. It often results from friction, pressure, or repeated motion between two surfaces.
• Types: Common forms include abrasive wear, adhesive wear, fatigue wear, and corrosive wear.
• Where it occurs: Found in mechanical parts like gears, bearings, seals, and sliding assemblies where two surfaces rub or slide against each other.

Erosion:

• Definition: Erosion involves material removal due to the repeated impact of high-speed particles or fluids striking a surface.
• Mechanism: Can result from solid particle flow, liquid droplet impingement, or cavitation effects in fluid systems.
• Where it occurs: Common in high-velocity systems such as turbines, valves, pump impellers, and piping exposed to slurry or gas streams.

Key Distinctions:

• Wear: Caused by surface contact and friction between solids.
• Erosion: Caused by fluid or particle impact without surface-to-surface rubbing.

Understanding whether a component is failing due to wear or erosion helps guide choices in coatings, materials, and system design to improve service life and performance.

Corrosion and erosion are both forms of material degradation, but they occur through entirely different mechanisms — one chemical, the other mechanical.

Corrosion:

• Definition: Corrosion is a chemical or electrochemical reaction between a material (usually metal) and its environment. It causes the material to deteriorate over time, often due to moisture, oxygen, acids, or salts.
• Examples: Rust formation on steel, silver tarnishing, or copper turning green with patina.

Erosion:

• Definition: Erosion is the physical removal of material caused by high-velocity fluids, solid particles, or droplets striking a surface. It is a purely mechanical process — no chemical reaction is involved.
• Examples: Turbine blade wear from steam flow, pipe wall thinning from slurry impact, or water eroding soil along a riverbank.

Key Differences:

• Process Type: Corrosion is chemical or electrochemical; erosion is mechanical.
• Trigger: Corrosion is caused by environmental reactions; erosion is caused by particle or fluid impact.

Explore erosive vs. corrosive metal failure to learn how to diagnose and prevent each type effectively.

Materials typically fail from four major types of wear:

• Abrasive wear occurs when hard particles or rough surfaces grind against a softer material, cutting or scraping away layers over time.
• Adhesive wear happens when two surfaces slide under pressure, causing small bits of material to transfer or tear away.
• Corrosive wear combines chemical attack with mechanical action — acids, moisture, or other corrosives weaken the surface, making it more prone to wear.
• Fatigue wear results from repeated stress cycles, which create microcracks that grow until chunks of material flake off.

Understanding the differences between wear types is key to selecting the right surface treatment or coating to extend part life.