Definition - What does Segregation mean?
Segregation is the separation of different types of atoms or molecules. Segregation in terms of material science can have two different meanings. One meaning is material segregation, which is when similar atoms or molecules within a material begin to congregate at discontinuities. Particle segregation is when volumes of materials separate from one another based on size and shape.
Corrosionpedia explains Segregation
Material segregation almost always occurs at discontinuities in a material. These discontinuities include grain boundaries, dislocations, laminations and pores. Material segregation can have very serious consequences if left unattended. Since material segregation increases the concentration of one type of molecule in a given area of a material, it creates material that is less homogeneous. This lack of homogeneity creates areas of material that do not have the intended chemical or mechanical properties. This can cause premature material failure. For example, if much of the iron in stainless steel were to segregate away from the chromium, then the stainless steel would most likely be more prone to rust in the area with the high concentration of iron.
Particle segregation is another type of segregation when talking in terms of material science. Particle segregation deals with entirely different bodies of materials, rather than the internal molecular structure. Particle segregation occurs through mechanical means. Particle segregation is important when a certain size, density or shape of a material is necessary for the application. An example of this is grit blasting prior to coating. If the grit material has not been uniformly segregated prior to being projected, then insufficient cleaning may occur, resulting in inadequate coating adhesion and ultimately base material failure. Alternatively, the substrate may acquire an incorrect surface profile.