What are the four main requirements for any corrosion reaction to occur?

Question

Are they anode, cathode.surface area and medium (air, water,etc.)

Four main requirements

Answer 1

The chemical deterioration of a material, usually a metal or metal alloy, is called corrosion. The most common causes of corrosion are contact with water and oxygen, though other substances in the earth and in the atmosphere can also cause corrosion. The material with the greatest economic importance that is most affected by corrosion is iron.

Anode and cathod comes into picture when a chemical is flowing through a piping and equipment with different MOC, Then GALVANIC CORROSION will occur.
Medium is also correct.In case of water which is a raw water and not treated, then there is a chances of SCC(stress corrosion cracking and local pittting).
Factoring affecting corrosion:
Material factor :
Bulk chemical composition,Microstructure ,Grain boundary composition ,
Surface condition .
Environment Factor :Nominal environment definition ,type,chemistry,concentration,phase,conductivity .
Local environment definition :
velocity ,thin layer wetting,wetting and drying cycles,heat transfer boiling ,
wear and fretting ,deposits.
Stress Factor :
Stress definition,mean stress,maximum stress,minimum stress,
constant load/constant strain,strain rate,plane stress/plane strain,modes I, II, II ,biaxial,cyclic frequency,wave shape .
Sources of stress :
intentional ,residual,corrosion wedging ,thermal cycling.
Geometry Factor :
Discontinuities which intensify stress ,Generation of galvanic potentials,
Chemical crevices ,Settling of solids,Restricted geometries leading to concentration cells .
Temperature Factor :
Time Factor :
Changes in GB chemistry:
Changes in microstructure:
Changes in surface deposits, chemistry or/and heat transfer resistance
Development of surface defects, pitting or/and erosion
Development of occluded cells.

Answer 2

In a word, gravity is the source of the heat and pressure needed to start and maintain nuclear fusion within the core of a star. To star nuclear fusion, hydrogen nuclei must be forced to move around so rapidly that when they hit each other, they fuse together instead of bouncing off each other. A bare hydrogen nucleus is positively charged, and two positively charged particles repel each other. But if they can be forced close enough to each other, they will combine into a heavier helium nucleus and release vast amounts of energy. Gravity is the force that makes this possible. It wants to collapse the star, but as the atoms in it get crowded together, they bounce off each other, and move about at a higher and higher velocity within the star, creating very high internal pressures and temperatures. In other words, as a gas is compressed, it heats up in the same manner as air that passes through a compressor does. If the mass is sufficient, eventually a collapsing proto star starts nuclear fusion and becomes a self-luminous star. Gravitational compression of the Sun's interior continued until nuclear fusion started in a violent outburst, causing the star to abruptly expand then contract until the inward pull of gravity reached a state of equilibrium with the outward pressure created by heat produced through nuclear fusion. From that point on, gravity keeps the Sun interior hot and dense enough for nuclear fusion to continue as long as there is fuel to sustain it. It serves to hold the star together and it serves to confine the fusing hydrogen so stable nuclear reactions can be maintained. Without the confining force of gravity, the Sun and other stars will then become gigantic hydrogen bombs that blow themselves apart the moment nuclear fusion begins.

Answer 3

Temperature, - Warm usually increases corrosion
Electrolyte, - Anode, Cathode
Oxygen, - exposure
Material, - what kind of medium?

there is more to it but I am not taking out my Haz-mat books, this is basic you can go from here.

Answer 4

Temperature, Oxygen, heat and reactive elements