Effective corrosion protection of 8090 alloy by cerium conversion coatings

Influence of Rare Earth Samarium/Ytterbium Salt on Electrochemical Corrosion Behavior of Aluminum-Based Anode for Batteries

In this work, effects and mechanism analysis of samarium acetate and ytterbium acetate on enhancing the electrochemical corrosion performance of aluminum-based anode for aluminum-air batteries in 3.5 wt.% NaCl are studied by methods such as weight loss tests, electrochemical measurements, anode galvanostatic discharge tests and microscopic morphology analysis. The results show that samarium acetate and ytterbium acetate are ideal electrolyte additives, and exhibit obvious inhibitory effects on the self-corrosion of 7075 aluminum alloy. The optimal concentration is 200 mg/L. Moreover, corrosion inhibitors mainly reduce the self-corrosion speed of aluminum by suppressing the microcathodic reaction, thereby promoting the improvement of the discharge performance of aluminum-air batteries. Simultaneously, it is found that after mixing samarium acetate and ytterbium acetate in different proportions, the two rare earth salts have a mutual adjustment effect. By adding different rare earth salt components, the battery capacity densities of the anode are improved by 9.6% to 16.3%. Finally, a possible model is presented to illustrate the impact mechanism of different additives on the self-corrosion process and discharge performance of aluminum-air batteries.

Surface Pretreatments of AA5083 Aluminum Alloy with Enhanced Corrosion Protection for Cerium-Based Conversion Coatings Application: Combined Experimental and Computational Analysis

The effects of surface pretreatments on the cerium-based conversion coating applied on an AA5083 aluminum alloy were investigated using a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), polarization testing, and electrochemical impedance spectroscopy. Two steps of pretreatments containing acidic or alkaline solutions were applied to the surface to study the effects of surface pretreatments. Among the pretreated samples, the sample prepared by the pretreatment of the alkaline solution then acid washing presented higher corrosion protection (~3 orders of magnitude higher than the sample without pretreatment). This pretreatment provided a more active surface for the deposition of the cerium layer and provided a more suitable substrate for film formation, and made a more uniform film. The surface morphology of samples confirmed that the best surface coverage was presented by alkaline solution then acid washing pretreatment. The presence of cerium in the (EDS) analysis demonstrated that pretreatment with the alkaline solution then acid washing resulted in a higher deposition of the cerium layer on the aluminum surface. After selecting the best surface pretreatment, various deposition times of cerium baths were investigated. The best deposition time was achieved at 10 min, and after this critical time, a cracked film formed on the surface that could not be protective. The corrosion resistance of cerium-based conversion coatings obtained by electrochemical tests were used for training three computational techniques (artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine regression (SVMR)) based on Pretreatment-1 (acidic or alkaline cleaning: pH (1)), Pretreatment-2 (acidic or alkaline cleaning: pH (2)), and deposition time in the cerium bath as an input. Various statistical criteria showed that the ANFIS model (R² = 0.99, MSE = 48.83, and MAE = 3.49) could forecast the corrosion behavior of a cerium-based conversion coating more accurately than other models. Finally, due to the robust performance of ANFIS in modeling, the effect of each parameter was studied.

A Study of the Localized Ceria Coating Deposition on Fe-Rich Intermetallics in an AlSiFe Cast Alloy

Corrosion inhibiting conversion coating formation is triggered by the activity of micro-galvanic couples in the microstructure and subsequent local increase in pH at cathodic sites, which in the case of aluminium alloys are usually intermetallics. Ceria coatings are formed spontaneously upon immersion of aluminium alloys in a cerium conversion coating solution, the high pH gradient in the vicinity of intermetallics drives the local precipitation of ceria conversion compounds. Cu-rich intermetallics demonstrate a highly cathodic nature and have shown the local precipitation reaction to occur readily. Fe-rich intermetallics are, however, weaker cathodes and have shown varied extents of localized deposits and are in focus in the current work. Model cast Al-7wt.%Si alloys have been designed with 1 wt.% Fe, solidified at different cooling rates to achieve two different microstructures, with big and small intermetallics, respectively. Upon subjecting the two microstructures to the same conversion coating treatment (immersion in a 0.1 M CeCl₃ solution) for a short period of 2 h, preferential heavy deposition on the boundaries of the big intermetallics and light deposition on the small intermetallics was observed. Based on these observations, a mechanism of localized coating initiation at these Fe-rich intermetallic particles (IM) is proposed.

Polymer Nanocomposite-based Coatings for Corrosion Protection

Corrosion of metals induces enormous loss of material performance and increase of cost, which has been a common and intractable issue that needs to be addressed urgently. Coating technology has been acknowledged to be the most economic and efficient approach to retard the metal corrosion. For several decades, polymers have been recognized as an effective anticorrosion coating material in both industries and scientific communities, as they demonstrate good barrier properties, ease of altering properties and massive production. Nanomaterials show distinctively different physical and chemical properties compared with their bulk counterparts, which have been considered as highly promising functional materials in various applications, impacting virtually all the fields of science and technologies. Recently, the introduction of nanomaterials with various properties into polymer matrix to form a polymer nanocomposite has been devoted to improve anticorrosive ability of polymer coatings. In this review article, we highlight the recent advances and synopsis of these high-performance polymer nanocomposites as anticorrosive coating materials. We expect that this work could be helpful for the researchers who are interested in the development of functional nanomaterials and advanced corrosion protection technology.

Effect of graphene oxide on anticorrosion performance of polyelectrolyte multilayer for 2A12 aluminum alloy substrates

Corrosion of aluminum alloys (Al alloys) has been a ubiquitous problem, and this seriously restricts its range of applications.

Polyorthotoluidine dispersed castor oil polyurethane anticorrosive nanocomposite coatings

Conducting polymer (polyorthotoluidine) dispersed castor oil polyurethane nanocomposite coatings were synthesized and show a remarkably higher corrosion resistant performance in alkaline medium.