COMPARISON OF CORROSION OF ALUMINUM-BASED ALLOYS FORMING DECAGONAL QUASICRYSTALS IN NaCl SOLUTION

Abstract

In this work corrosion behavior of the Al72Co18Ni10, Al65Co20Cu15, and Al72Fe15Ni13 alloys forming decagonal quasicrystalline phases was tested in the neutral NaCl solution (pH = 7) which allows a comparison of their corrosion resistance under conditions comparable to application in marine climate. The microstructure of the alloys was studied by quantitative metallographic, X-ray, scanning electron microscopic, and energy dispersive analyses. The corrosion properties were determined by gravimetric and potentiodynamic methods. The Al65Co20Cu15 and Al72Fe15Ni13 alloys have been established to corrode in the sodium chloride solution more strongly than the Al72Co18Ni10 alloy. The corrosion that proceeds under electrochemical mechanism is accompanied by the formation of passive layer on the surface that retards further dissolution in the saline solution after 3–4 days of testing. Scanning electron microscopy shows the marks of pitting corrosion. The pits appear mostly where flaws and boundaries of iron- or aluminum-rich crystalline phases are located. Their quantity and size are lesser on the surface of the Al72Co18Ni10 alloy since Co and Ni in its composition are rate determining for the corrosion processes. This alloy may be recommended as starting material for plasma-spayed coatings working in marine climate.