<p>Powder-processed Al-Cr-Mn-Co-Zr alloys containing icosahedral quasicrystalline dispersoids in an Al matrix exhibit exceptional pitting corrosion resistance, but the roles of the quasicrystal structure, chemistry, morphology, and distribution are unclear. Here, additive friction stir deposition (AFSD) has been used to produce fully dense deposits from one of these alloys using powder-processed material as the feedstock. The pitting resistance of the AFSD material was evaluated using ASTM standard salt-fog exposures and potentiodynamic polarization tests. The microstructures of the deposits and the salt-fog-exposed surfaces were characterized using a combination of X-ray diffraction, electron microscopy, and focused ion beam sectioning. The AFSD material contained no quasicrystals, but instead exhibited a fine uniform mixture of Al₄₅(Cr,Mn)₇, Al₉Co₂, and Al₃Zr phases in the Al matrix. During salt-fog exposures, the Al₄₅(Cr,Mn)₇ and Al₉Co₂ phases acted as cathodic sites promoting dissolution of the adjacent Al matrix and the formation of a corrosion product bilayer. This bilayer was composed of a graded fibrillar boehmite (AlOOH) inner layer and a dense polycrystalline bayerite (Al(OH)₃) outer layer. Samples exposed for 6&#xa0;weeks exhibited mean pitting potentials of + 1336&#xa0;mV; this is significantly higher than the values for the feedstock alloy (+ 794&#xa0;mV) and for the conventional Al alloys 6061 (−&#xa0;126&#xa0;mV) and 7075 (−&#xa0;706&#xa0;mV) tested under the same conditions. Since the corrosion product bilayer on the AFSD material resembled that formed on the feedstock alloy, these data indicate that it is the composition and dispersion of the cathodic phases, not the quasicrystalline structure, that leads to the formation of the protective and adherent corrosion product layers.</p> Graphical abstract <p></p>