Difference Between Corrosion and Rancidity

Edited by Diffzy | Updated on: April 30, 2023


Difference Between Corrosion and Rancidity

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When left exposed, metals react with air moisture, acids, and other atmospheric gases and deteriorate. Corrosion is the term for this interaction. Dish that contains fats and oil oxidise when exposed to air, giving the food a terrible flavour and smell. Rancidity is the term for this interaction.

Corrosion vs Rancidity

The primary distinction between corrosion and rancidity is that the cycle of rust formation in metal caused by barometric dampness and synthetics is known as corrosion. On the other hand, food that has gone rotten is no longer wanted. This phrase describes the damage that oxygen does to food.

The utilisation of electrochemical cycles to separate mixtures into components or to create new mixtures can be both painful and advantageous. Corrosion is a typical end result of electrochemical reactions between different materials and substances in their current state. Consumption is a risky and very expensive problem. It can cause structures and platforms to collapse, oil pipelines to burst, designed facilities to fail, and bathrooms to flood.

The term "rancidity" refers to the complete or incomplete hydrolysis or oxidation of fats and oils when exposed to air, light, moisture, and bacterial action; this primarily occurs in food items leaving them unfit for use. In a broader sense, foods that include oil and unsaturated fats are frequently associated with rancidity. All that is left of unsaturated fats is fat, cholesterol, and steroids.

Difference Between Corrosion and Rancidity in Tabular Form

Parameters of Comparison Corrosion Rancidity
Happenings relates to metals. relates to eating.
Occurrence the metal and oxygen reaction. . the interaction of oxygen and food fats
Time slower tempo quicker procedure
Example  corrosion of iron Too long was the butter left out in the open.
Changes  physical alterations  Unable to eat and has a terrible odour

What is Corrosion?

When reacting to another substance, such as oxygen, hydrogen, electrical flow, or even soil and microscopic life, metal consumes. When steel or other metals are put under a lot of pressure and the substance breaks, corrosion can also occur. The most well-known type of iron corrosion occurs when it is exposed to oxygen and the presence of water, creating a red iron oxide that is commonly referred to as rust.

Steel and other iron composites are susceptible to rust. Iron can also rust when it reacts with chloride in an oxygen-deprived environment, whereas green rust, another type of corrosion, can be made directly from metallic iron or iron hydroxide. The ongoing biological interaction on the material surface causes corrosion of both metals and nonmetals.

This partnership has an effect on buildings and offices made of different materials. In fact, even the surrounding air, which is heavy in oxygen and moisture, can start the chemical reaction known as rusting on steel surfaces. Corrosion is also accelerated by burning soft drink residue and the vapour of acids like sulphur corrosive.

However, because of aluminium, the oxide coating formed by the underlying destructive attack protects the surface from further harm. Corrosion can occur on surfaces that are lowered below the water line as well as surfaces that are drifting above the water line in marine environments where airborne salt crystals are stored aboard ships. Corrosion affects the materials' microstructure, mechanical characteristics, and outward appearance. Rusting and other types of degradation reduce the capacity of pipes and equipment, resulting in the loss of output, equipment loss, or even life.

Corrosion is one of the most frequent phenomena we see on a daily basis. You've surely seen that certain iron things develop an orange or reddish-brown coating over time. Rusting, a sort of corrosion, causes a chemical reaction that results in the formation of this layer.

Refined metals are changed by corrosion into more stable compounds such metal oxides, metal sulphides, and metal hydroxides. The interaction of air moisture and oxygen with iron results in the formation of iron oxides. Because it compromises the beneficial properties of the metal, corrosion is frequently seen as a negative process.

For instance, the stiffness and tensile strength of iron are well known (especially alloyed with a few other elements). Contrarily, rusting makes iron objects brittle, flaky, and structurally unsafe. Because it frequently involves redox reactions between the metal and specific atmospheric agents like water, oxygen, and sulphur dioxide, among others, corrosion is an electrochemical process.

Corrosion-Affecting Factors

  • Airborne gases including CO2, SO2, and SO3 are exposed to metals.
  • metals that have been exposed to water, especially saltwater (which increases the rate of corrosion).
  • There are impurities, such as salt (e.g. NaCl).
  • Temperature: Corrosion accelerates as the temperature rises.
  • initial oxide layer's makeup: certain oxides, such Al2O3, provide an impermeable protective layer that can halt further corrosion. For instance, rust easily disintegrates and reveals the remaining metal.
  • Acidic atmosphere: Acids have the power to accelerate the corrosion process.

Corrosion Types

The many kinds of corrosion include the following:

  • When there is a difference in ionic concentration between any two local areas of a metal, a specific type of corrosion known as crevice corrosion can take place. Crevice corrosion can happen in gaskets, on washer undersides, and on bolt heads. For instance, crevice corrosion happens in stainless steels and aluminium alloys of all grades.
  • Stress-Related Corrosion Cracking: Corrosion SCC is the term used to describe when metal breaks due to a combination of tensile stress and a corrosive environment. When the temperature is hot, it occurs frequently. Stress corrosion cracking of austenitic stainless steel is one example of what might happen in a chloride solution.
  • Intergranular Corrosion: Intergranular corrosion results from the presence of impurities in the grain boundaries that separate the grain produced during the solidification of the metal alloy. It can also be brought on by depletion or enrichment of the alloy at these grain boundaries. IGC, for instance, affects alloys with an aluminium basis.
  • Galvanic corrosion can happen when an electric contact forms between two metals that have different electrochemical compositions and are situated in an electrolytic environment. It talks about how one of these metals breaks down at a joint or junction. This type of corrosion is well-illustrated by the deterioration that takes place when copper and steel come into contact in a saltwater environment. When carbon steel and aluminium are joined and immersed in saltwater, the aluminium corrodes more quickly.
  • Pitting Corrosion: Pitting Corrosion is difficult to detect since it is erratic and unpredictable. It is thought to be one of the riskiest types of corrosion. Starting in one place, it spreads until a corrosion cell is formed, which is enclosed by the normal metallic surface. The "Pit" continues to grow after it has been created and can assume many different forms. If the pit is left unattended, metal from the surface is gradually eaten away in a vertical direction, eventually leading to structural failure. Think about a water droplet on a steel surface. Pitting will start close to the droplet's centre (anodic site).
  • The most frequent type of corrosion, uniform corrosion occurs when the environment assaults the metal's surface. It is easy to observe how far the rust has spread. The performance of the material is little impacted by this type of corrosion. Normally, a piece of steel or zinc would dissolve uniformly throughout its surface when submerged in dilute sulfuric acid.

What is Rancidity?

Food must be kept from becoming bad in order to maintain its beneficial qualities. All that is left of unsaturated fats is fat, cholesterol, and steroids. These have a lengthy aliphatic chain and are carboxylic acids. They can either be unsaturated, with several links between carbon atoms, or saturated, with a single linkage between carbon molecules. Getting food products away from direct light and air contact is probably the easiest way to prevent them from rotting.

They can therefore be stored in containers that are both airtight and watertight. A potent technique for preventing auto-oxidation activity in food sources containing fats and oils is to include cell reinforcements. Cell reinforcements come in both natural and artificial forms. L-ascorbic acid, vitamin E, flavonoids, and polyphenols are common cell reinforcements.

Sequestering specialists like EDTA also prevent or reduce oxidation, and so can prevent rancidity. Linseed oil, which is converted into stinky oil, serves as a good example because it is frequently used to harden oil-based paints, such as craftsman's "oil" paints. Similar to how the polymer arrangement of these oxygenated unsaturated fats causes the solidifying reaction. Pecan oil is also known to quickly turn rancid. Polyunsaturated unsaturated fat oils should be stored in the refrigerator to reduce the response for this particular explanation.

Similar to how some people react strongly to pecans that have developed even a slight odour, One won't eat any nuts that smell just a little bit "wrong" since the thought of some kind of polymers forming in the stomach is very horrifying.

Rancidity-Affecting Factors

  • Oxidation: The main cause of rancidity is the oxidation that follows from this exposure, as lipids are eight times more soluble in oxygen than in water. The majority of the oxidation of unsaturated lipids is mediated by free radicals. These chemical reactions can result in highly reactive molecules in rancid foods and oils, which are the source of the offensive and poisonous flavours and odours. This process is known as auto-oxidation, sometimes called oxidative rancidity.
  • Triglycerides react with water to produce diglycerides and free fatty acid residues during hydrolysis. Diglycerides react with water to produce monoglycerides and fatty acids. The monoglycerides finally underwent complete hydrolysis, releasing glycerol and fatty acids. Rancidity caused by hydrolysis is what this is.
  • Lipase, a hydrolytic enzyme generated by certain bacteria, directly obstructs the breakdown of triglycerides into glycerols and fatty acids when microorganisms are present. The auto-oxidation of these fatty acids causes them to become bad. The proper pH and other factors are necessary for microbial lipase to function on fats and oils.

Rancidity Types

  • Rancidity that develops in foods as a result of oxygen damage is known as "oxidative rancidity." In this, the fats are oxidised and decomposed into compounds with shorter carbon chains, such as fatty acids, aldehydes, and ketones. These are volatile and contribute to the rancid fat's unpleasant odour. During the process, oxygen molecules interact with the oil's natural structure. This leads to the change in odour and taste. In oxidised fat, there are three categories of chemicals that have been shown to be toxic:
  • fats that have undergone peroxidation (peroxidized fatty acids destroy both vitamin A and E in foods).
  • polymer-based materials (under normal food processing conditions these appear in small enough quantities to be insignificant).
  • Sterols that have undergone oxidation (thought to be involved in the causation of atherosclerotic disease).
  • Enzymatic breakdown of fats causes the release of free fatty acids from glycerides, which produces a rancid odour. Rancidity caused by hydrolysis is what this is. Hydrolysis removes the fatty acid chains from the glycerol backbone in glycerides. Oxidative rancidity is a result of the free fatty acids' continued auto-oxidation.

Main Difference Between Corrosion and Rancidity in Points

  • While rancidity is associated with food sources, corrosion is associated with metals.
  • While rancidity refers to the reaction of dietary lipids with oxygen, corrosion involves the contact of metals with oxygen and moisture.
  • Additionally, the rancidity cycle is quicker than the corrosion cycle.
  • For instance, rusting is a form of erosion in which iron is consumed by the action of air and moisture, leaving a ruddy, earthy-colored layer of iron oxide as a frame. Another example is rancidity, which occurs when margarine is kept open for an extended period of time and results in a change in taste and smell.
  • While rancidity has a more severe impact, such as an unpleasant smell or flavour, rust primarily affects the physical structure of the substance.


Rust forms when metal interacts with air moisture and synthetic materials, which is referred to as corrosion. The term "rancidity" refers to a state in which food has turned unpleasant. It is frequently used to represent how much oxygen is present in oils. This phrase describes the damage that oxygen does to food.

The typical structure of the food is affected when oxygen particles combine with the oil and food, changing the fragrance and flavour, and it isn't advised for consumption. The point at which a bag of chips is exposed to barometric air and the flavour and smell change is an example of rancidity.



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"Difference Between Corrosion and Rancidity." Diffzy.com, 2024. Mon. 17 Jun. 2024. <https://www.diffzy.com/article/difference-between-corrosion-and-rancidity-673>.

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