There's no rust in the desert..why?

Question

There's no rust in the desert..why?

Answer 1

Rust usually requires water.

Answer 2

Rust is a general term for a series of iron oxides, usually red oxides, formed by the reaction of iron with oxygen in the presence of water or air moisture.  Other metals undergo equivalent corrosion, but the resulting oxides are not commonly called rust.  When in contact with water and oxygen, or other strong oxidant or acids, iron will rust.  Given sufficient time, oxygen, and water, any iron mass eventually converts entirely to rust and disintegrates.

Desert environments are arid (in other words, they lack humidity and are very dry.)  Where there is no water, there is no rust.  It is true that salt in the environment can hasten the formation of rust.  However, the answer to the question is that there MUST be water in order to form rust.

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If you want the scientific answer, see below. (CAUTION - highly technical answer ahead!)

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The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen.[4] The rate of corrosion is affected by water and accelerated by electrolytes, as illustrated by the effects of road salt (calcium chloride) on the corrosion of automobiles. The key reaction is the reduction of oxygen:

O2 + 4 e- + 2 H2O → 4 OH-

Because it forms hydroxide ions, this process is strongly affected by the presence of acid. Indeed, the corrosion of most metals by oxygen is accelerated at low pH. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows:

Fe → Fe2+ + 2 e−

The following redox reaction also occurs in the presence of water and is crucial to the formation of rust:

2 Fe2+ + 0.5 O2 → 2 Fe3+ + O2−

Additionally, the following multistep acid-base reactions affect the course of rust formation:

Fe2+ + 2 H2O ⇌ Fe(OH)2 + 2 H+

Fe3+ + 3 H2O ⇌ Fe(OH)3 + 3 H+

as do the following dehydration equilibria:

Fe(OH)2 ⇌ FeO + H2O

Fe(OH)3 ⇌ FeO(OH) + H2O

2 FeO(OH) ⇌ Fe2O3 + H2O

From the above equations, it is also seen that the corrosion products are dictated by the availability of water and oxygen. With limited dissolved oxygen, iron(II)-containing materials are favoured, including FeO and black lodestone (Fe3O4). High oxygen concentrations favour ferric materials with the nominal formulae Fe(OH)3-xOx/2. The nature of rust changes with time, reflecting the slow rates of the reactions of solids. Furthermore, these complex processes are affected by the presence of other ions, such as Ca2+, which both serve as an electrolyte, and thus accelerate rust formation, or combine with the hydroxides and oxides of iron to precipitate a variety of Ca-Fe-O-OH species.

Answer 3

Not enough moisture,  no rainfall.  

Thousands or old airplanes are stored in the Mojave Desert.  Some planes can be ready to fly again in a short time.

Answer 4

zero humidity.

Answer 5

There certainly is rust in the desert.  It just progresses very slowly because of the dryness.  Rust requires water.  If you keep a piece of steel perfectly dry, it doesn't rust.  But there is always some water vapor in the air, and even in the dryest desert it rains from time to time.

Answer 6

because theres no salt