How to remove corrosion at home

Metallic, non-metallic coatings and other methods of protection

[Deposit Photos]

Cor­ro­sion is the spon­ta­neous de­struc­tion of met­al un­der the im­pact of the en­vi­ron­ment. Any fac­tors can have a neg­a­tive im­pact on met­al – chem­i­cal, physi­co-chem­i­cal, elec­tro­chem­i­cal. Not only pure met­als are sub­ject to cor­ro­sion – many al­loys may also rust.

How the rust­ing process takes place

Met­al cor­ro­sion can be ob­served quite fre­quent­ly in open air in a damp en­vi­ron­ment – in­sol­u­ble com­pounds form on the sur­face, ox­ides (as a re­sult of con­tact with oxy­gen), car­bon­ates (from re­ac­tion with car­bon diox­ide CO₂ in the air), and sul­fides of the cor­re­spond­ing met­al. A typ­i­cal ex­am­ple of rust­ing is the ap­pear­ance of red­dish-brown coat­ings on steel ob­jects (the ox­ide and hy­drox­ide of the triva­lent iron forms). The equa­tion of the process is the fol­low­ing:

4Fe + 6H₂O + 3O₂ = 4Fe(OH)₃ (iron(III) hy­drox­ide – an in­sol­u­ble base of a red­dish-brown col­or)

When this re­ac­tion takes place, ac­cess of air and mois­ture mak­ing con­tact with the met­al sur­face are suf­fi­cient. As Fe(OH)₃ in this form is quite an un­sta­ble com­pound, it swift­ly los­es wa­ter, form­ing the ox­ide Fe₂O₃:

2Fe(OH)₃ = Fe₂O₃ + 3H₂O

Iron(III) ox­ide is not an ox­ide film which can pro­tect the met­al from fur­ther de­struc­tion. The for­ma­tion does not stop sub­se­quent ox­i­da­tion of the met­al on the sur­face of Fe₂O₃, so if the rust is not re­moved in time, the met­al may be de­stroyed com­plete­ly.


This does not hap­pen with all met­als – in the cor­ro­sion process, some (for ex­am­ple alu­minum) are cov­ered with a thick ox­ide film, which pro­tects the met­al sur­face from fur­ther de­struc­tion. Only af­ter its re­moval, the met­al be­gins to re­act with the en­vi­ron­ment again

4Al + 2H₂O + 3O₂ = 4AlO(OH) (the white flaky sub­stance alu­minum metahy­drox­ide forms)

Low re­ac­tive met­als (for ex­am­ple, cop­per, which is cov­ered with a pati­na, a green­ish coat­ing) cor­rode much more slow­ly and weak­ly than ac­tive ones. No­ble met­als are bare­ly dam­aged at all un­der the im­pact of the en­vi­ron­ment – gold Au, sil­ver Ag, plat­inum Pt etc.

How to re­move rust at home

Traces of rust of­ten ap­pear on the sur­face of iron ob­jects. If de­struc­tion has be­gun re­cent­ly, and the sur­face of the met­al is not dam­aged too great­ly, then rust can be re­moved at home.

Of­ten the sim­plest method is used to do this – the me­chan­i­cal re­moval of rust by a rough met­al brush. To achieve the ef­fect more quick­ly, you can pre­pare a paste of bak­ing soda or hy­dro­gen per­ox­ide (or wa­ter) with cream of tar­tar, rub the sur­face of the met­al with the paste, and then rub it off. For large ob­jects, rough sand­ing equip­ment and ma­chines are used. They work ac­cord­ing to the same prin­ci­ple as rough brush­es – when the disk ro­tates, the rust is re­moved. It is im­por­tant to re­move the cor­ro­sion care­ful­ly, as it is pos­si­ble that the ma­chine may dam­age the clean sur­face of the met­al.

Any acids are es­pe­cial­ly good for re­mov­ing rust – by re­act­ing with iron ox­ides and hy­drox­ides, they dis­solve un­want­ed for­ma­tions.


Gen­er­al­ly, there are a few sim­ple meth­ods for re­mov­ing rust with acids:

  • soak­ing in ap­ple vine­gar (you sim­ply have to im­merse the ob­ject in the vine­gar so­lu­tion overnight, and then re­move the rust with a piece of crum­pled foil; it can also be rinsed with vine­gar);
  • soak­ing in lemon or lime juice (to re­move traces of cor­ro­sion more ef­fec­tive­ly, you can sprin­kle the met­al sur­face with ta­ble salt, rinse with lemon or lime juice, and leave for a long time; af­ter­wards, as is the case with vine­gar, rub the rust off with crum­pled foil);
  • soak­ing in hy­drochlo­ric or phos­phor­ic acid (it is of­ten en­coun­tered in ev­ery­day life, and works against cor­ro­sion quite ef­fec­tive­ly). The or­thophos­pho­ric acid con­tained in Coca Cola means it can also be used to re­move rust from met­al.

Rust can be re­moved from small ob­jects by plac­ing a pota­to on a metal­lic sur­face or stick­ing an ob­ject into a pota­to – the ox­al­ic acid con­tained in pota­toes also pro­vides ef­fec­tive pro­tec­tion against cor­ro­sion.

Spe­cial liq­uids are use­ful for re­mov­ing rust from met­al – you can sim­ply ap­ply them to the rusty sur­face, and then re­move the rust af­ter a short time. They usu­al­ly have quite a tox­ic com­po­si­tion, so fol­low in­struc­tions and ob­serve safe­ty rules.

Met­al can also be cleaned us­ing elec­trol­y­sis – pre­pare a so­lu­tion of bak­ing soda (1 ta­ble­spoon per 4 liters of wa­ter). As an an­ode, you can use a piece of steel (it should be at­tract­ed by a mag­net; alu­minum or stain­less steel won’t be suit­able). To the part of the an­ode which is above the so­lu­tion, at­tach the pos­i­tive clamp of the ca­ble, and to the non-rusty part of the cleaned ob­ject, the neg­a­tive clamp (it is im­por­tant that the clamp and ca­ble are not in the so­lu­tion). Af­ter con­nect­ing the ca­ble to the bat­tery, you can turn on the sys­tem. Af­ter 8–12 hours the re­ac­tion will take place, and the ob­ject can be re­moved, turn­ing off the pow­er be­fore­hand – all the rust will come away from the met­al and gath­er on the steel. But the met­al will prob­a­bly have to be cleaned with a rough brush from the re­mains of the ox­ides.

How to pro­tect met­als from cor­ro­sion

There are sev­er­al meth­ods for pre­vent­ing the de­struc­tion of met­als un­der the im­pact of the en­vi­ron­ment. They do not give a 100% re­sult – cor­ro­sion pro­cess­es can only be stopped com­plete­ly in an at­mos­phere of in­ert gas­es (for ex­am­ple ar­gon). In most cas­es this is im­pos­si­ble.

Met­al coat­ings

The main method of com­bat­ting cor­ro­sion is plac­ing var­i­ous coat­ings on the sur­face of met­al (metal­lic, non-metal­lic, chem­i­cal). Metal­lic coat­ings come in two types:

  • an­ode (cov­er­ing a less ac­tive met­al with a more ac­tive one – for ex­am­ple, cov­er­ing iron with zinc);
  • cath­ode (cov­er­ing a more ac­tive met­al with a less ac­tive one – such as cov­er­ing iron with cop­per).

An im­por­tant dif­fer­ence in these types of coat­ings is that when an an­ode coat­ing is used, the pro­tect­ed met­al is en­tire­ly pre­served, un­til the coat­ing is not com­plete­ly worn away. With the cath­ode method, a sin­gle in­stance of dam­age to the film is suf­fi­cient for the pro­tect­ed met­al to start to dis­in­te­grate.

Non-metal­lic coat­ings

Non-metal­lic coat­ings usu­al­ly in­clude poly­mer mass­es, non-or­gan­ic and or­gan­ic com­pounds – for ex­am­ple, var­nish­es, paints, ce­ment and glass-like mass­es. They have a much low­er re­ac­tive abil­i­ty, and so they keep the met­al in­tact.

[Deposit Photos]

Chem­i­cal coat­ings

Chem­i­cal pro­tec­tion from cor­ro­sion means cre­at­ing a durable film on the sur­face of met­al, which does not al­low the met­al to dis­in­te­grate. These films can be ob­tained by the fol­low­ing meth­ods:

  • ni­tro­gena­tion – sat­u­rat­ing the metal­lic sur­face with ni­tro­gen;
  • ox­i­da­tion – cre­at­ing durable ox­ide films (for ex­am­ple, Al2O₃, BeO);
  • phos­pha­tiz­ing – cre­at­ing a phos­phate pro­tec­tive film (such as Fe₃(PO₄)₂).

Such meth­ods of chem­i­cal pro­tec­tion from cor­ro­sion as bur­nish­ing and ce­men­ta­tion are also wide­spread. In the first case, there is a re­ac­tion of the sur­face of the met­al with or­gan­ic sub­stances, and in the sec­ond the for­ma­tion of car­bon com­pounds on the sur­face

Elec­tro­chem­i­cal pro­tec­tion

Met­al can be pro­tect­ed elec­tro­chem­i­cal­ly. Some­times a pro­tec­tive kind is mind – a plate of a more ac­tive met­al is at­tached to the met­al ob­ject (in this case this met­al is the pro­tec­tor). The more ac­tive met­al has a low­er po­ten­tial, and so is an an­ode. When a cur­rent is run it starts to dis­in­te­grate, while the pro­tect­ed met­al (in this case the cath­ode) is pre­served un­dam­aged.

If you at­tach the pro­tect­ed met­al to the cath­ode (neg­a­tive­ly charged elec­tron) of the source of the di­rect cur­rent, the pro­tect­ed met­al it­self be­comes a cath­ode. In this case it is not the cath­ode that will dis­in­te­grate, but the an­ode (scrap met­al is used as the an­ode – as it dis­in­te­grates, it pre­serves the cath­ode from de­struc­tion).

Oth­er meth­ods of pro­tec­tion


In some cas­es, it helps to add com­pounds to the met­al which in­crease its dura­bil­i­ty to cor­ro­sion (the tech­ni­cal com­po­si­tion of the ma­te­ri­al changes, and the pre­served met­al does not cor­rode as strong­ly as it would in pure form). Oth­er met­als are also used as ad­di­tives which are less prone to rust­ing, or non-or­gan­ic or or­gan­ic com­pounds.

In­hibitors of cor­ro­sion are sub­stances that pre­vent and stop met­al dam­age. Usu­al­ly, adding them changes the prop­er­ties of the en­vi­ron­ment the met­al is in, mak­ing it fa­vor­able for keep­ing the sur­face in­tact. Var­i­ous sub­stances may be used as in­hibitors – de­pend­ing on the type of met­al and cause of cor­ro­sion. For ex­am­ple, to pre­vent iron rust­ing, potas­si­um bichro­mate or amines may be in­tro­duced into the en­vi­ron­ment, if it is damp. Click here for amaz­ing ex­per­i­ments with iron.

In some cas­es, in­hibitors are not in­tro­duced, but more ag­gres­sive el­e­ments that cause cor­ro­sion are re­moved from the en­vi­ron­ment (for ex­am­ple ex­cess mois­ture). When us­ing home meth­ods of rust re­moval, it is im­por­tant to ob­serve cau­tion, as this of­ten in­volves work­ing with caus­tic sub­stances. All me­chan­i­cal abra­sives are quite rough, so one should work in pro­tec­tive gloves to avoid scratch­es.