Permeation

In physics and engineering, permeation is the penetration of a fluid through a solid. Permeation is modeled by equations such as Fick's laws of diffusion. It can be measured using tools such as a minipermeameter. The permeability of metals is much lower than that of ceramics and polymers due to their crystal structure and porosity. A good tire is one that allows the least amount of gas to escape. Water vapour permeation can be important for submarine cables to protect the conductor from corrosion. Pipes intended to transport water under high pressure can be considered failed when there is a permeation of water through a pipe. The number and size of the individual fuel cells depends on the permeation through the pipe and on the power output of the stack, which depends on both the size and the number of individual cells in the stack. A material can be semipermeable, with the presence of a semiper meable membrane. Only molecules or ions with certain properties will be able to diffuse across such a membrane. This is a very important mechanism in biology where fluids inside a blood vessel need to be regulated and controlled.