Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen. Formation of an oxide of iron due to oxidation of the ironatoms in solid solution is a well-known example of electrochemical corrosion, commonly known as rusting. This type of damage typically produces oxide(s) and/or salt(s) of the original metal. Corrosion can also refer to other materials than metals, such as ceramics or polymers. Although in this context, the term degradation is more common.

In other words corrosion is the wearing away of metals due to a chemical reaction.

Many structural alloys corrode merely from exposure to moisture in the air, but the process can be strongly affected by exposure to certain substances (see below). Corrosion can be concentrated locally to form a pit or crack, or it can extend across a wide area more or less uniformly corroding the surface. As corrosion is a diffusion controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the exposed surface, such aspassivation and chromate-conversion can increase a material’s corrosion resistance. However,some corrosion mechanisms are less visible and less predictable

Condensation

Condensation is the change of the physical state of aggregation (or simply state) of matter from gaseous phase into liquid phase and the reverse ofevaporation.^[1] When the transition happens from the gaseous phase into the solid phase directly, bypassing the liquid phase, the change is calleddeposition. While condensation can occur in many different substances, the condensation of water vapor in air is by far the most common experienced (such as the formation of dew on a cold drink).

Condensation commonly occurs when a vapor is cooled to its dew point, but the dew point can also be reached through compression. The condensed vapor is called a condensate, the laboratory or the industrial equipment used for condensation is called a condenser.

The science of studying the thermodynamic properties of moist air and the interrelationships between these in order to analyze, and predict properties by changing in the conditions of moist air is called psychrometry. The interrelationship can be graphically represented, and prediction carried out graphically by the psychrometric chart. Most people think the water is condensation, but condensation is only the process of change.

Water vapor that naturally condenses on cold surfaces into liquid water is called dew. Water vapor will normally only condense onto another surface when the temperature of that surface is cooler than the temperature of the water vapor.

The magnetic state (or phase) of a material depends on temperature (and other variables such as pressure and applied magnetic field) so that a material may exhibit more than one form of magnetism depending on its temperature, etc.

Erosion is a natural process, but it has been increased dramatically by human land use, especially industrial agriculture, deforestation, and urban sprawl.^[1][2] Land that is used for industrial agriculture generally experiences a significant greater rate of erosion than that of land under natural vegetation, or land used for sustainable agricultural practices. This is particularly true if tillage is used, which reduces vegetation cover on the surface of the soil and disturbs both soil structure and plant roots that would otherwise hold the soil in place. However, improved land use practices can limit erosion, using techniques such as terrace-building, conservation tillage practices, and tree planting.

A certain amount of erosion is natural and, in fact, healthy for the ecosystem. For example, gravels continuously move downstream in watercourses. Excessive erosion, however, causes serious problems, such as receiving water sedimentation, ecosystem damage and outright loss of soil.

Erosion is distinguished from weathering, which is the process of chemical or physical breakdown of the minerals in the rocks, although the two processes may occur concurrently.

Erosion

Severe soil erosion in a wheat field near Washington State