Aluminum alloys corrosion chloride-containing solutions

Instrumentation. The experimental procedure for an AFM equipped with a suitably coated tip has been outlined above. In a study of an aluminum alloy AA2024-T3, intermetallic particles and the matrix phase could be separated clearly [98]. The different surface films on these phases could be associated with their corrosion behavior. Inclusions and their corrosive behavior have been studied with a combination of SKPFM and AFM [101]. The effect of chloride-containing solution on corrosion at the matrix and the intermetallic particles was studied with SKPFM, in addition, light scratching with the AFM in the contact mode was applied to study the effect of the mechanical destabilization [102]. The intermetallic particles dissolved immediately after the film on their surface had been destabilized by mechanical abrasion. 

Although the application of WBE system described by Tan et al. in REM-based corrosion inhibitor research has not been reported, a similar multi-electrode method has been used for the evaluation and selection of REM-based corrosion inhibitors. Muster et al. described a rapid screening approach for the evaluation of candidate corrosion inhibitors including REM compounds. Garcia et al. used this multi-electrode system to study the influence of pH on corrosion inhibition of AA2024-T3 aluminum alloy in O.lMNaCl solution containing potassium dichromate, cerium dibutylphosphate and cerium chloride. 

ALUMINUM CHLORIDE. AlClj. Anhydrous aluminum chloride has been stored and transported in aluminum alloy containers. Moist aluminum chloride and aluminum chloride solutions are very corrosive to aluminum alloys. The severity of attack depends upon the quantity of free hydrochloric acid produced by hydrolysis and on the temperature. See also Ref (1) p. 125. (2) p. 37. (3) p. 77. (7) p. 11. 

FIGURE 14.22 Local admittance maps on the model couple after 2h of immersion (a) without deeano-ate (0.001 M Na2S04) and (h) in a solution containing 0.05 M sodium decanoate. Frequency = 1 Hz (pH 6, chloride-free electrolyte). (Reprinted from Electrochim. Acta, 55, Boisier, G., Portail, N., and Pehere, N., Corrosion inhibition of 2024 aluminum alloy by sodium decanoate, 6182 (eolor online). Copyright 2010, with permission from Elsevier.)... 

Davoodi et al. have predominantly used their SECM-AFM probes to investigate localized corrosion processes [51-56], Initial studies focused on the aluminum alloy AA1050. Dissolution was initiated by anodically polarizing the sample in a solution containing chloride ions (lOmM NaCl) and the redox mediator, IJ [51]. Ij was turned over to 1 at sites where the aluminum alloy started to corrode and the SECM-AFM tip was biased at a potential to detect 1. In this way, it was possible to correlate images of the corroding surface with redox activity, as shown in Figure 17.11. Preliminary results indicated that enhanced local dissolution may occur well below the breakdown potential, but only for a small fraction of the surface area. 

Metal Coatings. Tellurium chlorides, as well as tellurium dioxide in hydrochloric acid solution, impart permanent and attractive black antique finish to silverware, aluminum, and brass. Anodized aluminum is colored dark gold by tellurium electro deposition. A solution containing sodium tellurate and copper ions forms a black or blue-black coating on ferrous and nonferrous metals and alloys. Addition of sodium tellurite improves the corrosion resistance of electroplated nickel. Tellurium diethyldithiocarbamate is an additive in bright copper electroplating (see Electroplating). 

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