Corrosion deterioration, definition

On the other hand, corrosion has been defined as the undesirable deterioration of a metal or alloy, i.e. an interaction of the metal with its environment that adversely affects those properties of the metal that are to be preserved. This definition —which will be referred to as the deterioration definition —is also applicable to non-metallic materials such as glass, concrete, etc. and embodies the concept that corrosion is always deleterious. However, the restriction of the definition to undesirable chemical reactions of a metal results in anomalies which will become apparent from a consideration of the following examples. 

Corrosion is the deterioration of a substance or its properties because of a reaction with its environment. For our purposes, we can be a little more precise in this definition therefore, corrosion is a destructive attack of a metal by either chemical or electrochemical reaction with a given environment [183J. 

In the case of non-metallic materials, the term corrosion invariably refers to their-deterioration from chemical causes, but a similar concept is not necessarily applicable to metals. Many authorities consider that the term metallic corrosion embraces all interactions of a metal or alloy (solid or liquid) with its environment, irrespective of whether this is deliberate and beneficial or adventitious and deleterious. Thus this definition of corrosion, which for convenience will be referred to as the transformation definition. 

Definition of corrosion in the context of Corrosion Engineering the reaction of an engineering constructional metal (material) with its environment with a consequent deterioration in properties of the metal (material). 

The enormous scope of the subject of corrosion follows from the definition which has been adopted in the present work. Corrosion will include all reactions at a metal/environment interface irrespective of whether the reaction is beneficial or detrimental to the metal concerned —no distinction is made between chemical or electropolishing of a metal in an acid and the adventitious deterioration of metal plant by acid attack. It follows, therefore, that a comprehensive work on the subject of corrosion should include an account of batteries, electrorefining, chemical machining, chemical and electrochemical polishing, etc. 

Corrosion is the deterioration of a material by reaction with its enviromnent. Although the term is used primarily in conjunction with the deterioration of metals, the broader definition allows it to be used in conjunction with all types of materials. We will limit the description to corrosion of metals and alloys for the moment and will save the degradation of other types of materials, such as polymers, for a later section. In this section, we will see how corrosion is perhaps the clearest example of the battle between thermodynamics and kinetics for determining the likelihood of a given reaction occurring within a specified time period. We will also see how important this process is from an industrial standpoint. For example, a 1995 study showed that metallic corrosion costs the U.S. economy about 300 billion each year and that 30% of this cost could be prevented by using modem corrosion control techniques [9], It is important to understand the mechanisms of corrosion before we can attempt to control it. 

Particularly under the broad definition of corrosion as the deterioration of materials by reaction with the environment, the number of mechanisms whereby deterioration occurs is large. In general, a mechanism of corrosion is the actual atomic, molecular, or ionic transport process that takes place at the interface of a material. These processes usually involve more than one definable step, and the major interest is directed toward the slowest step that essentially controls the rate of the overall... 

Corrosion is the deterioration a material undergoes as a result of its interaction with its surroundings. Although this definition is applicable to any type of material, it is usually reserved for metallic alloys. Of the 105 known chemical elements, approximately eighty are metals, and about half of these can be alloyed with other metals, giving rise to more than 40,000 different alloys. Each of the alloys will have different physical, chemical, and mechanical properties, but all of them can corrode to some extent, and in different ways. 

Corrosion may be defined as the spontaneous deterioration of a structure or part of a structure due to the action of the total environment or individual environmental agents. For the purposes of this chapter, the structure is assumed to be metallic and the environment is assumed to be aqueous. Using this definition and the constraints noted, this chapter will outline the electrochemical techniques used to develop criteria of corrosion and those used in the study of corrosion kinetics. 

Why deterioration and not corrosion In fact, the definition of corrosion is based on anodic and cathodic reactions. These reactions make sense only when applied to metals. Therefore, corrosion is a terminology that is normally used for metals. 

Definition Mixt. of calcium hydroxide and sodium and/or potassium hydroxide Properties Wh. or grayish wh. gran. partly sol. in water almost completely sol. in 1M acetic acid rapidly deteriorates on exposure to air Toxicology Toxic by ing., inh. corrosive irritant to skin, eyes, mucous membranes Precaution Incompat. with trichloroethylene which is decomposed by warm alkali to produce a toxic end prod. absorbs CO2 from air... 

Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with its environment. Deterioration by physical causes is not called corrosion, but is described as erosion, galling, or wear. In some instances, chemical attack accompanies physical deterioration, as described by the following terms corrosion-erosion, corrosive wear, or fretting corrosion. Nonmetals are not included in this definition of corrosion. Plastics may swell or crack, wood may split or decay, granite may erode, and Portland cement may leach away, but the term corrosion, in this book, is restricted to chemical attack of metals. 

This introductory section includes basic definitions related to chemical and electrochemical reactions in the forward (f) and reverse (r) directions. The word Corrosion stands for material or metal deterioration or surface damage in an aggressive environment. Corrosion is a chemical or electrochemical oxidation process, in which the metal transfers electrons to the environment and undergoes a valence change from zero to a positive value z. The environment may be a liquid, gas or hybrid soil-liquid. These environments are called electrolytes since they have their own conductivity for electron transfer. 

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