PROTECTIVE LAYERED ELECTRODEPOSITS

The development of multilayered coatings as a means of enhancing perfo rmance, especially corrosion service life, has its origins in hot dipp ed diffusional coating process. Such coatings develop two or three lay ers having thicknesses of 1-20 mum (''macro'' layered coatings), or th ickness of 10-1000 nm (''micro'' layered coatings). The layered charac ter enables enhancement of physical and mechanical properties to be ac hieved thereby widening product application ranges. Distinction can be made between compositionally and structurally modulated layered coati ngs, and a number of examples are cited.