Protective ability of lamellar coatings in chemically and biologically active media

The paper compares the protective ability of lamellar coatings with various filler metals (zinc, aluminum and zinc-aluminum lamellas, as well as lamellas: metal powder combinations), binders (titanium oxide, epoxy and Teflon) and various structures (single-layer and two-layer coatings with various kinds of filler metals and binders).The expediency of using protective lamellae for protection in biologically aggressive environments is shown.It is shown that the amount of electrochemically active zinc added to lamellar coatings increases the protective ability of coatings by the same amount.When a fraction of zinc is replaced by a small amount of aluminum (3-7%), the protective mechanism changes dramatically from 100% sacrificial mechanism to the prevailing barrier protection (γbar ≈ 70%); the reasons for such a sharp change in the mechanisms of action and the reasons for the increase in the protective ability of such coatings are revealed in exhaustive detail and substantiated.It is shown that in the two-layer coatings under study, the contribution of the barrier mechanism is 8-16% greater than in singlelayer coatings due to the misalignment of the pore network in the first and second layers, as a result of which the interface between these layers plays the role of a "locking" layer.