Chromium-Free Conversion Protective Coatings on 1424 Aluminum Alloy

Abstract—It is known that lithium-containing aluminum alloys possess low pitting corrosion resistance. It has been previously shown that an IFKhANAL-3 alkaline chromate-free conversion composition gives the coatings on a series of aluminum alloys, such as AMg3, D-16, and V95, which are comparable to conventional chromate coatings in terms of protective properties. It should also be noted that inhomogeneous CCs that do not adhere to the substrate are formed in standard chromate conversion composition on lithium-containing alloys; therefore, development of the method for the fabrication of protective CC for 1424 alloy is a relevant task. In this work, the effect of various complexing agents on the oxidation and protective properties of the coatings based on 1424 alloy have been studied. The modifying additives under study have decreased the concentration of different oxides in the conversion compositions providing adsorption of corrosion inhibitors and increase in their protective properties. According to the results of accelerated corrosion tests, integrated use of Trilon B and BTA significantly increases the corrosion resistance of the coatings based on 1424 alloy.