Good day to you all, thanks for always reading my post. It is another moment to discuss two related terms "rust and corrosion". Are these two terms the same? we will get to find an answer to the pending question in the article.

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Pixabay, CC0 Creative Commons, Deteriorated roof by corrosion

I traveled to my hometown during the course of the weekend to see my mother. When I got to a hill called Mapo Hill in Ibadan, I saw at a distance far away that almost all the buildings that my eyes captured have a brownish roofing. I had a thought in my mind that it could be that the community involved decided to have a common colour of roofs but as I moved closed I found out that the roofs were suffering from corrosion, humm, no, rusting. Then I didn't actually know which of the terms to use because I do hear people using the two words to mean the same. But I later found out the right words to use after I made a personal finding about these two terms of discussion.
The process of removing the effects of corrosion and rust shall also be discussed in this article.

Let set the ball rolling

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What is Corrosion?

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By Thester11 - Own work, CC BY-SA 3.0, Corrosion on exposed metal

Corrosion occurs when there is a reaction of a material over a particular time with its environment which in turn deteriorates the structure of the material and further breaks it down into pieces. It can even break it down to its level of atom i.e. atomic level. Corrosion is a natural process which occurs when material most especially metal reacts with its external environment thereby resulting into oxidation of the metal when exposed to the atmospheric oxygen. Materials other than metals like ceramics and polymer can also experience degradation.

Corrosion of metals is caused by many external factors such as water, salt, bases, acids and some chemicals which can exist as solid or liquid. Besides these, gaseous chemical like ammonia gas, formaldehyde gas, acid vapor and sulfur gas can result into corrosion of metal. Corrosion process occurs on the basis of an electrochemical reaction. Anodic and cathodic reactions usually occur in a metal in which corrosion is taking place. Some materials are liable to experience corrosion while some are resistant to corrosion. However, there are various methods by which corrosion can be prevented. One of the common methods is the coating of the material. This coating can occur through painting, application of enamel on the surface, plating and so on.

Any substance other than iron that undergoes deterioration in strength, appearances and quality has just undergone corrosion like those corroded roofs I saw on my way to my hometown.

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RUST

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By Roger McLassus, CC BY-SA 3.0, Rust and dirt on a baking plate

On the other hand, rust occurs only with iron substances to produce its oxides by the process known as oxidation. Oxidation is simply explained as the addition of oxygen to a material which occurs mainly by exposure of materials to ambient air. When this occurs, there is a total change in both the physical appearance and chemical constituents. Simply put, rusting occurs when a metal which contains iron experience the process of corrosion. Various elements such as Moisture, water, salt etc do react with iron to form the oxides of iron (rust).

The chemical reaction that takes place during rusting is an oxidation reaction which converts iron into Ferric Oxide. During this oxidation process, the iron is oxidized to Fe(II) and later to Fe(III). Rust is made up of hydrated iron (II) oxide (Fe2O3.nH2O) and iron (III) oxide-hydroxide (FeO(OH), Fe(OH)3 ). Apart from iron, rusting does occur to any metals that contain iron (alloys). Transfer of electron from iron to oxygen is the starting reaction for rusting. This results in the formation of iron (II) ions.

Fe → Fe²⁺ + 2 e−
In the presence of water, hydroxide ions are formed from oxygen by accepting an electron
O₂ + 4 e– + 2 H₂O → 4 OH–
Presence of acid and electrolyte like salt increase rate of the above reaction. The above formed Fe (II) ions are further oxidized to Fe (iii) ions since Fe(iii) ions is contained in rusting. Below is how Fe (iii) ions are formed from Fe (ii) ions
4 Fe²⁺ + O₂→ 4 Fe³⁺ + 2 O₂-
The following acid-base reaction is being undergone by Fe (III) ions and Fe (II) ion
Fe²⁺ + 2 H₂ O ⇌ Fe(OH)₂ + 2 H+
Fe³⁺ + 3 H₂ O ⇌ Fe(OH)₃ + 3 H+

Finally, during rusting, there is a formation of a series of hydrated iron oxides
Fe(OH)₂ ⇌ FeO + H₂ O
Fe(OH)₃⇌ FeO(OH) + H₂O
2 FeO(OH) ⇌ Fe₂O₃ + H2O

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Removal of rust and corrosion

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Both the rust and corrosion can be removed with the same processes and methods despite the fact they are a bit different. There are various methods of removal but I will only discuss two methods here; Acidic removal method and electrolysis process

REMOVAL BY ACIDIC SOLUTION

First method is the use of acidic solution to remove both corrosion and rust. The following are the various acidic solution that can be used to remove both corrosion and rust.

• Application of vinegar: This solution called vinegar works effectively like magic when applied to a rusted surface. In order to use this as rust/corrosion removal, dip wholly inside a vinegar the rust material overnight and in the following morning scrape the rust part away with an aluminum foil structured into a crumpled ball like. It is advisable to use apple cider vinegar in order to achieve a better result. Although, white vinegar also work but not as effective as apple cider vinegar. At times, the rust material might need to stay inside the vinegar for like complete a day depending on the intensity of the rust in order to achieve the best result.

• Application of lime or lemon juice: These two work perfectly especially in the removal of rust stains on cloth. If a rusted metal is soaked into these two juices for a long time, the rust can be removed too. Dip very well in a lemon or lime juice the rust material which has been sprinkled with salt and leave it for enough time. After that, use a crumpled-up aluminum ball to scrape away the rust.

• Application of phosphoric acid or hydrochloric acid: These acids are effective rust removal and are inexpensive chemical. Phosphoric acid is present in naval jelly, molasses and cola drinks. Application of phosphorus acid to any rust item turns the iron oxide into a ferric phosphate. Leave overnight a solution of phosphoric acid in which the rust material is immersed. Allow it to dry and scrape away the ferric phosphate on it.

• Hydrochloric acid: Hydrochloric acid is present in many home cleaning agents especially in toilet cleaners. In steel industry, it is often used to remove scale or rust. After application of hydrochloric acid and rinsing, it keeps on working. It can also discolor some other metals that happened to be in the same room. If this happened, heat the affected metal in an oven or fire.

By Chad Randl - Public Domain, removal of corrosion

ELECTROLYSIS PROCESS
In this process, there are procedures to follow in order to remove rust from a metal. Discuss below are the procedure involved in the electrolysis process.

• Prepare an electrolyte solution: Prepare this solution by dissolving one tablespoon of washing soda or baking soda per gallon of water. Use water that is enough to submerge the rust material. It is preferable to make use of warm water and not cold water to enhance easier and homogenous solution of the soda.

• Use different metal as an anode (sacrificial piece): Anode is the part of the electrolytic cell that the rust from the rusted material clings to. It is called sacrificial piece because it will be sacrificed for the rust metal to become clean. Half of the size of this anode must be dip in the solution and unto the other half is attached the positive terminal. Therefore, your anode must be big. Note: the second half of the anode must be above water.

• The rusted material is connected to the negative terminal: Look for rust –free part on the rusted object (cathode) and connect the negative terminal from the battery charger to it. In order to achieve better connection, the negative terminal must be attached to rust free portion on the rusted object. In a case where you can’t find a rust free part on the cathode, scrape away some rust from the metal. Dip the whole rusty object into the solution and make sure it doesn’t get in contact with the anode and keep away the wire from the solution.

• The positive terminal is connected to the sacrificial metal: Here, the positive terminal which is red in color is attached to the sacrificial metal. Don’t forget half of the anode must be in water while the other half must be outside.
  Turn on the car battery charger: With this, you have actually started the electrolysis process which might take up to 20 hours. Make sure you first turn off and unplug the battery charger in case you want to check the status of the rusted object.

• Unplug and disconnect the battery charger: At this juncture, you would have achieved a rust-free object. Still, you have to clean it with Scotch Brite pad and bristle brush. Sludges on the object are being removed by the Scotch Brite while the harder to reach spot is removed by bristle brush.

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Conclusion

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With my few explanations, I think by now we should be able to differentiate between corrosion and rust. Also, we should be able to remove rust/corrosion from materials. It is better to prevent corrosion or rust, there are many ways of preventing corrosion/rust which includes; Surface coating by painting, Electroplating/electropolishing, Anodic and cathodic protection e.t.c.

Thanks For reading

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References

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1. https://en.wikipedia.org/wiki/Rust
2. https://www.differencebetween.com/difference-between-corrosion-and-vs-rusting/
3. https://www.quora.com/What-is-the-difference-between-corrosion-and-rusting
4. https://www.wikihow.com/Remove-Rust-and-Corrosion
5. https://www.apartmenttherapy.com/how-to-clean-rust-off-old-loaf-141206