Abstract
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.
Highlights
Lightweight materials such as aluminum alloys are attractive for applications in many different industries, including automobile, aviation, aerospace, biological implants, and sports equipment [1]
The effect of different pretreatments on the formation of cerium conversion coating applied to AA5083 is investigated, and corrosion behavior of coated AA5053 plates is studied in 3.5 wt.% NaCl
The goal is to find how different pretreatments influence the formation of the cerium conversion layer and how it controls the corrosion of AA5083
Summary
Lightweight materials such as aluminum alloys are attractive for applications in many different industries, including automobile, aviation, aerospace, biological implants, and sports equipment [1]. These results state that cerium oxide behaves as cathodic inhibitor for aluminum alloys They claimed that by increasing time of immersion in Ce containing solution up to 30 min, Icorr of coated samples decreased but after 30 min the parameter increased. This study evaluates the corrosion resistance of ceriumbased conversion coating on aluminum alloy 5083, prepared at acid and alkaline surface pretreatment conditions. Based on the dataset of inhibitory power obtained by the experimental test results, three soft computing models were adopted to build a model for simulating the corrosion resistance of coated Al-alloys at various pretreatment conditions. %) were used as a metallic substrate to study the effect of pretreatment on corrosion behavior and cerium coating quality deposited on the alloy surfaces. After selecting the best surface pretreatment, various deposition times were investigated (1, 5, 10, and 20 min) to find the suitable deposition time in the cerium bath
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