Rust is a type of oxidative corrosion, specifically affecting iron and its alloys. When iron reacts with oxygen and water, it forms iron oxide, commonly known as rust. This process can be classified under uniform corrosion because it usually affects the metal surface uniformly, but it can also lead to more localized forms if the conditions vary across the surface.
metal failure mode
metal failure mode
Uniform Corrosion
Learn key variables and mitigation tips for uniform corrosion
uniform corrosion overview
What is Uniform Corrosion?
Uniform corrosion is a type of general corrosion that occurs evenly across the entire surface of a metal or alloy. At first glance, the corrosion mechanism can cause an unwanted appearance, leading to the gradual loss of material and potential weakening of the material structure. This corrosion mechanism is often observed in mechanical systems exposed to a variety of environments, such as automotive, construction, and chemical processing applications.
Uniform corrosion can be defined as the process of metal loss that occurs at a uniform rate over the entire exposed surface, resulting in a reduction of material thickness and potentially compromising the structural integrity. Synonymous terms for uniform corrosion include general corrosion and even corrosion.
What Causes Uniform Corrosion?
Several factors influence the occurrence and progression of uniform corrosion in industrial applications and mechanical systems, such as:
-
Surface Condition
The condition of the exposed surface, such as cleanliness, roughness, and presence of surface defects, can impact the uniformity of the corrosion process.
-
Electrochemical Factors
The electrochemical properties of the material, such as galvanic potential and corrosion potential, can influence the rate of corrosion by determining the electrochemical reactions that occur on the surface.
-
Environment
The chemical composition, temperature, humidity, and pH of the environment can affect the aggressiveness of the corrosion process, influencing the extent of corrosion.
-
Protective Surface Films
The presence and stability of protective surface films, such as oxide layers, can affect the uniform corrosion rate and the material’s resistance to corrosion.
Mitigating Uniform Corrosion
To reduce the progression of uniform corrosion in machined components, the mitigation strategies outlined below should be taken into consideration:
-
Material Selection
Work with materials that have suitable properties, such as high corrosion resistance and appropriate chemical compatibility, to reduce the propensity for corrosion.
-
Protective Coatings
Apply functional coatings with high corrosion resistance, such as electroless nickel, thin dense chrome, or organic based coatings to provide a protective barrier to corrosion. Hybrid coatings that combine nickel and chromium, such as Armoloy Bi-Protec, can be even more effective at protecting components against corrosive forces.
-
Surface Preparation
Ensure proper surface preparation, including cleaning, degreasing, and removal of surface defects, to promote uniformity of the protective films and reduce the likelihood of localized corrosive attack.
Armoloy's Solution to Corrosion
Armoloy offers multiple metal surface treatments with varying levels of protection from the common causes of corrosion. Offering both broad-spectrum and industry-specific applications, our protective metallic coatings add significant value through increased performance and decreased revenue losses from unplanned maintenance and downtime.
Our protective coatings ensure a thin, precise coat that won’t impact production, but will improve surface hardness and prevent environmental defects. Beyond increasing wear life, Armoloy tailors our metallic coatings based on the specific requirements of your application and industry.
While uniform corrosion is a widespread and detrimental failure mechanism, it’s fairly easy to accurately predict and employ mitigation techniques to effectively control. Understanding the key variables that impact corrosion, along with choosing the right materials and protective surface coatings, can dramatically reduce the likelihood of machined components experiencing failure from corrosive actions.
Beyond the Lab: Metal Failures in Narrative Form
Other Metal Failure Modes
Other common metal failures include:
Corrosion can also result from, or be a precursor to, other potential metal failures
Frequently Asked Questions
Corrosion wear, also known as corrosive wear, is a type of material degradation that involves both chemical and mechanical processes. Here’s a detailed explanation:
Definition: Corrosion wear occurs when materials are subjected to simultaneous chemical attack and mechanical wear. This dual action accelerates the degradation process compared to corrosion or wear occurring independently.
Mechanism: The process starts with the chemical reaction between the material surface and corrosive agents (such as acids, alkalis, or salts). This reaction weakens the surface by forming corrosion products. Mechanical action, such as abrasion or erosion, then removes these weakened layers, exposing fresh material to further corrosion. This cyclical process leads to rapid material loss and surface damage.
Examples: Corrosion wear is common in environments where machinery is exposed to harsh chemicals and abrasive particles, such as in chemical processing plants, marine applications, and mining operations.
Prevention: To mitigate corrosion wear, use corrosion-resistant materials, apply protective coatings, ensure proper lubrication, and control the environment to reduce exposure to corrosive agents. Regular maintenance and monitoring are also essential to detect early signs of wear and take corrective actions.
By understanding and addressing both the chemical and mechanical aspects of corrosion wear, the lifespan of components can be significantly extended.
Corrosion:
- Definition: Corrosion is the chemical or electrochemical reaction between a material, typically metal, and its environment, leading to the gradual deterioration of the material. This process often involves the material reacting with oxygen, moisture, acids, or other chemicals.
- Examples: Rusting of iron, tarnishing of silver, and patina formation on copper.
Erosion:
- Definition: Erosion is the physical removal of material from a surface due to mechanical action, such as the impact of solid particles, liquid droplets, or high-velocity fluid flow. Unlike corrosion, erosion is a purely mechanical process.
- Examples: Wear of turbine blades by high-velocity steam, riverbank erosion by water flow, and wind erosion of soil.
Key Differences:
- Nature: Corrosion is a chemical process, whereas erosion is a mechanical process.
- Causes: Corrosion is caused by chemical reactions, while erosion is caused by physical forces.
Partner With Us
Eliminate corrosion from your operations. Meet our group of curious, innovative engineers and learn how we can help improve your industry with science-based solutions.