Unearthing 5 Unexpected and Threatening Causes of Corrosion

We are all familiar with the sight of rusted iron structures or the green patina on copper roofs – visual manifestations of corrosion. Yet these instances barely skim the surface of a much broader phenomenon, affecting various materials under diverse conditions.

We explore 10 corrosion causes in another post, but here are 5 unexpected and unnoticed sources of corrosion.

These unseen forms of corrosion/rust often quietly eat away at our structures and devices, causing far-reaching repercussions. These sources of corrosion defy conventional wisdom.

A Confluence Of Elements: Defining Corrosion

Corrosion is the natural process of transforming refined metals into a more stable mineral state—it’s nature’s way of reclaiming what was taken from it–albeit slowly yet relentlessly. This usually occurs through electrochemical reactions to their environment where metals lose electrons, undergoing oxidation.

Corrosion is not confined merely to physical degradation; it also indicates energy loss, which renders metal ineffective for fulfilling its initial purpose of structural support in buildings or electric current in wires.

This inherent propensity amongst metals towards self-destruction (from our practical perspective), coupled with its broad-ranging implications, makes rust an issue of paramount importance, causing detailed understanding and effective management strategies.

It extends beyond oxidation reactions with water and oxygen, penetrating many aspects of our daily life. Corrosion isn’t just about surface reaction; it’s an in-depth chemical process that occurs anytime, anywhere, given the right conditions. 

Although we commonly associate corrosion with damp environments or industrial settings, it can be caused by several seemingly harmless factors we encounter daily. Such unsuspected sources surround us – from our bodies to household items and atmospheric particles.

An Unseen Catalyst: Understanding How Surprising Sources Contribute to Corrosion

The chemistry behind corrosion might seem complex, yet it unveils surprising sources contributing to this process. Traditional forms of rust involve electrochemical reactions between metals or other susceptible materials and substances in their environment—typically water or oxygen—leading to deterioration.

However, many factors beyond moisture and oxygen trigger corrosive action, accelerating the process or starting it under conditions where traditional triggers may not work, leading to unexpected corrosion sources.

These surprising catalysts are often substances or elements that contain ions (charged particles), which expedite the exchange of electrons in the corrosion reaction.

For instance, salts, acids, and bases are rich in ions and promote corrosion. But these are not the only substances capable of influencing corrosive processes; a panoply of unsuspected sources lurk around us with the potential to incite or aggravate corrosion.

Surprising Source 1: The Unseen Damage of Sweat and Skin Oils

Human sweat in a gym leads to corrosion.

Would you be surprised to learn that everyday exposure to human sweat and skin oils is a significant source of corrosion, especially for metal objects? Human sweat is primarily water but contains various salts, proteins, fatty acids, and other organic compounds.

When these substances come into contact with metals such as iron or steel, they form a thin film on the surface, eventually leading to corrosion. Skin oil acts similarly.

It works as an electrolyte that speeds up the electrochemical reactions leading to corrosion. The salt content in human sweat further enhances this reaction because it conducts electricity.

Individual variations in body chemistry, diet, exercise habits, and personal hygiene practices influence the corrosive potential of sweat and skin oils. The process is slow but insidious: individual droplets of sweat or traces of skin oil may have little immediate effect.

They accumulate over time under conditions that prevent evaporation or removal through cleaning processes – such as in crevices or under tightly fitted parts – causing significant damage. 

Gym Equipment: Strengthening More than People

Gyms present a classic example where sweat and skin oils frequently come into contact with metallic surfaces.

From dumbbells to treadmill handles to weight machines, gym equipment sees heavy use by many individuals each day—each person leaves traces of their unique chemical signature via their sweat and skin oils.

Although many gym attendees are conscientious about wiping down equipment after use, hundreds if not thousands of users’ accumulated effects still lead to notable corrosion, particularly in crevices and other hard-to-clean areas. This degrades the equipment’s appearance and compromises its structural integrity.

Given the potential liability issues related to equipment failures, many gym owners are now investing in corrosion-resistant materials for their exercise machines or implementing stricter cleaning protocols to mitigate this risk.

Surprising Source 2: The Culinary Catalysts – Food and Beverages

To the untrained eye, your dinner plate may seem harmless. A closer inspection, however, unveils an insidious reality.

Foods and beverages, particularly those acidic or high in salts, act as catalysts for corrosion when they come into contact with metal surfaces. 

This is because they accept electrons in a process known as redox reactions. Arguably, one of the most familiar forms of this reaction occurs in battery acid or car batteries; similar principles also apply to certain food and drink items.

As metals interact with these substances, they oxidize—simply put, they rust. These processes occur at a microscopic level but, over time, lead to significant damage.

How often does food come into direct contact with metal outside of cutlery and cookware?

Consider soda cans lining supermarket shelves or the foiled wrapping enveloping fast-food burgers—both instances where food and metal interface directly.

A Fruity and Acidic Affair 

Citrus fruits like oranges and lemons are charged with citric acid, a known accelerant for corrosion when coupled with metals such as copper or zinc, commonly found in water pipes or household decorations.

Similarly perilous is vinegar.

Often used as a cleaning agent assumed to be harmless because of its natural basis, it’s packed full of acetic acid, which eagerly reacts with stainless steel surfaces, causing deterioration.

The danger isn’t limited to fresh produce either; canned foods also play their part in this corrosive symphony—they’re usually laced with salt that boosts conductivity, promoting oxidation processes within the cans when exposed to moisture.

While this might stir unease, it’s important to remember that these corrosive effects occur over time. Occasional contact poses minimal risk, but consistent exposure leads to perceptible damage.

Surprising Source 3: Atmospheric Pollutants

Acidic soil levels lead to corrosion.

Airborne contaminants play a pivotal role in corrosion. These atmospheric pollutants come in various forms, ranging from gaseous emissions to tiny particulates suspended in the air. They interact with macro and micro materials, often leading to unforeseen corrosive damage.

The corrosive effects of these airborne pollutants are intensified in the presence of moisture, a catalyst enabling their interaction with surfaces. Even seemingly impervious materials, such as stainless steel or aluminum, fall prey to these invisible aggressors’ insidious impact.

The pervasiveness of airborne contaminants means no environment is completely safe from this corrosion. Their intangible nature makes it nearly impossible to fully prevent their damaging effects without employing specific protective measures designed to combat atmospheric pollution.

Smog and Industrial Emissions: Silent Corrosion Agents

Smog and industrial emissions stand as two prominent contributors to airborne pollution-induced corrosion. High in sulfur compounds and particulate matter, these emissions are harmful because of their chemical reactivity.

Certain industries, such as power plants and manufacturing facilities, frequently emit large amounts of sulfur dioxide—a gas known for its potent corrosivity when combined with water vapor. This results in acid rain, which harms exposed metallic surfaces.

Smog is another ingredient to create corrosion.

Similarly, smog, an unhealthy mix comprising primarily smoke, soot, and other particulates, carries harmful substances like nitrogen oxides that become reactive under certain conditions.

The sheer pervasiveness and density of smog in urban areas mean it has a colossal impact on metal structures over extended periods.

Pollen and Organic Particulates: The Ignored Adversaries

While the corrosive effects of smog and industrial emissions are often highlighted, less attention is paid to the naturally occurring airborne contaminants, such as pollen and organic particulates, that facilitate corrosion. However, these elements are just as damaging in certain circumstances.

Organic particulates, microscopic remnants of plants, fungi, and other natural materials, accumulate on surfaces. In the presence of moisture, they foster an environment conducive to microbial growth, contributing to a unique form of corrosion known as Microbially Influenced Corrosion (MIC).

Similarly, pollen grains – microscopic particles released by flowers for reproduction – carry proteins that trigger chemical reactions leading to corrosion when settled on certain materials.

While this effect is typically localized rather than widespread, it underscores the diverse range of atmospheric pollutants capable of causing corrosion.

Surprising Source 4: Soil Composition

The world beneath our feet is teeming with an array of variables, each contributing to the diverse properties of soil.

In corrosion, soil composition plays a significant role. The physical and chemical properties of soil influence its corrosive behavior immensely, affecting buried metallic structures.

Soil Acidity or Alkalinity: The Invisible Catalyst

The pH value is a quantitative measure showing the acidity or alkalinity in substances, including soil. It runs on a scale from 0 to 14, with values below 7 being acidic and above 7 being alkaline. A neutral pH value is 7, common for pure water.

In soils with high acidity (low pH), ions like hydrogen (H+) concentration increases. These ions readily participate in electrochemical reactions that expedite metal corrosion.

Conversely, soils with high alkalinity often contain carbonates and bicarbonates that weaken metal surfaces, reducing their tendency to rust. Notably, both pH extremes enhance corrosivity—acidic soils through increased ion activity and alkaline soils through electrochemical reactions involving carbonate/bicarbonate ions.

Moisture Content: Feeding Corrosion One Drop at a Time

Moisture forms another crucial aspect in understanding the corrosive behavior of soils — it provides an environment wherein electrolyte flow facilitates electrochemical reactions leading to corrosion.

In simple terms, water in the soil allows the flow of ions between anodic and cathodic areas on a metal surface. This ion exchange is a prerequisite for corrosion to occur.

Areas with high rainfall or groundwater levels are often associated with increased soil corrosivity. However, it’s not merely the presence of water that escalates corrosion, but its interaction with other soil constituents such as oxygen, salts, and microorganisms further intensifies the process.

Surprising Source 5: Unseen Yet Everywhere: Microorganisms

Despite their diminutive size, microorganisms play a monumental role in corrosion. These biological entities- bacteria and fungi, to name a few- have astonishingly diverse metabolic capacities.

Some are aerobic, using oxygen for respiration, while others are anaerobic – not requiring oxygen at all. This diversity in metabolic pathways allows them to survive in a wide range of environments, and surprisingly, some even thrive on metallic substrates, causing microbial or bio-corrosion

In such cases, the corrosive process is facilitated by the metabolic activities of these microorganisms rather than the direct action of environmental factors on the metal.

For instance, certain strains of sulfate-reducing bacteria (SRB) generate sulfide as a byproduct, which reacts with metals like iron to form iron sulfide, a compound known for its corrosive impact.

SRBs are notorious culprits behind corrosion in industries dealing with oil extraction and water treatment, where they often form a biofilm (complex microbial communities) on pipelines and storage tanks. Another group called acidophilic bacteria oxidizes certain minerals, releasing acidic products that further corrode metals such as copper and aluminum. 

This phenomenon has been observed extensively in mining sites where these bacteria accelerate corrosion rates drastically. Knowing that our battle with corrosion is against physical elements and these invisible biological agents is crucial.

In Sum

Corrosion is an omnipresent phenomenon driven by diverse factors beyond our usual suspects, like water or air exposure. Understanding this complexity is vital for effective prevention strategies.

From sweat-drenched gym equipment to microorganism-laden pipelines or sulfur-rich soils – it’s clear that corrosion has an intricate tapestry of causes, and recognizing these less-known contributors is an essential first step. The good news is that innovation thrives in corrosion prevention and management.

Novel materials, coatings, and technologies are being continually researched and developed to tackle these challenges. As we continue to deepen our understanding of this complex phenomenon, we move closer to a world where we minimize the damaging effects of corrosion.

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