When iron reacts with oxygen, a series of compounds are formed that accumulate on the metal surface, giving rise to what we know as rust. The best home methods for eliminating it include mechanical removal via abrasion and the use of chemical-based reagents acidssuch as citric and acetic acid present in lemon juice and in thewhite vinegarwhich interact with rust compounds, facilitating their dissolution and removal.
Rust is a set of compounds that form fromoxidation of iron and the alloys that contain it. The term “oxidation” indicates a chemical reaction where iron atoms with atmospheric oxygen in the presence of water, which facilitates the electrochemical reactions responsible for corrosion. From these reactions, compounds such as oxides And hydroxides of iron, which progressively accumulate on the surface of the metal forming overlapping layers. The outermost part is typically of brownish-red color and is more crumblythat is, it tends to crumble easily. In the deeper layers, usually darker, there are more oxides, often hydratethat is, they integrate water molecules into their crystalline structure.
How to deal with rusty iron
How to eliminate rust with the main remedies: hand tools
To remove rust with mechanical methods, various solutions can be used:
Wire brush
Ideal for removing surface rust and coarse residues. It is the basic manual method (requires gloves and protective glasses).
Grinder
The most powerful tool, indicated for large areas or stubborn rust. It serves to bring the metal back to bare, but must be used uniformly so as not to gouge the surface.
Sandpaper
Perfect for small repairs, bends and finishing touches. We move from coarse to fine grain to leave the metal smooth and ready for painting.
How to clean rust with chemicals and natural home methods
In addition to representing an aesthetic problem, rust weakens the metalmaking it more fragile: for this reason it is important to treat it as soon as possible and in the correct way. In general, the way to get rid of it consists of two phases: first the superficial layer is eliminated, then chemical intervention is carried out on the deeper layers, which are more adherent and difficult to remove. In the domestic sphere, various tricks are known “do it yourself“, spread on the internet, such as the creation of pastes based on coarse salt or bicarbonate mixed with lemon juice or white vinegar.
Salt and baking soda play a role mild abrasive action: their particles, rubbed vigorously against the rust, allow it to be removed superficial layerthe most crumbly one.
Lemon and white vinegar are aqueous solutions which contain, respectively, citric acid And acetic acid. In chemistry, acids are substances capable of releasing into aqueous solution hydrogen ions (H+), i.e. positively charged hydrogen atoms. Precisely this characteristic allows them to react with the iron and oxygen compounds contained in rust, forming new compounds that adhere less to the metal and can be eliminated more easily. It is no coincidence that we often hear about how Coca-Cola can also be used as a home remedy for rust removal: this is thanks to its chemical composition, which contains phosphoric acid (H3BIT4), which can provide hydrogen ions.
Be careful though, because by mixing a base and an acid (for example bicarbonate and citric acid) these they neutralize each other: it would therefore be more appropriate to first use bicarbonate to eliminate the surface layer, and only then use the acid.
There are also specific products for rust removal, available in specialized shops such as hardware stores, containing acids such asoxalic acid ol’tannic acid.
Generally, acids should be kept in contact with rust to at least 30 minutesso as to have the necessary time to act. Small objects can be directly immersed in the liquid, but if the rust is found on large surfaces, such as those of a car, the acid can be applied with a brush, even in multiple layers.
Because acids remove rust
To understand how acids remove rust, we must remember a fundamental principle: chemical reactions in solution depend on the interactions between charged species and electrical charges of opposite signs attract each other. It should be emphasized that the real process is more complex and depends on many factors, such as type of acid and reaction conditions. However, we can describe the main mechanisms without going into too technical details.
Acids in water release H ions+: they therefore lose a positive charge and what remains consequently forms an anion with negative charge. In chemistry we say that acid is dissociatedthat is, it was split into two simpler parts. Both dissociation products play a key role in rust removal. H ions+ released by the acid react with the iron oxides and hydroxides of the rust, literally “dismantling” them: from the reaction water and iron ions are obtained in solution, which depending on the electrical charge can be distinguished into ferrous ion (Fe2+) And ferric ion (Fe3+).
This is where the parts of dissociated acid with a negative charge come into play, perfect for interacting with the positive charges of the iron: they in fact “surround” the iron ions forming chemical complexesstructures that allow iron to remain more easily in aqueous solution. This reduces the possibility of the iron settling on the surface again, forming new rust, making removal more effective.
