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Smart Coatings for Corrosion Protection
Published in Vaibhav Sanjay Kathavate, Pravin Pralhad Deshpande, Smart Coatings, 2023
Vaibhav Sanjay Kathavate, Pravin Pralhad Deshpande
Apart from this, anodized coatings provide a decorative finish to the underlying metal substrate and enhance the bonding ability between primer and metal. Anodizing of metals is generally performed in chromate or sulphuric acid solution. During chromate assisted anodizing via electrochemical deposition, metals are immersed into an aqueous solution of chromic acid (CrO3) at room temperature for 40–60 min at predetermined current levels. However, the same treatment is also applicable for sulphuric acid–mediated anodizing at a temperature not exceeding 20°C. The typical thickness of coatings produced by anodizing ranges from 8 to 30 µm depending upon the applied current and deposition time.
Surface Failure
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
Numerous precautions may be taken into account by a designer to reduce wear damage. Appropriate choice of materials and lubricants, cleanliness of the surfaces, and avoiding stress concentrations are among the most common remedies. Proper surface finish and hardness, strength to reduce abrasion, and increased surface life are necessary. Corrosive surroundings need special materials and thus coatings should be considered in some applications. Aluminum alloys often undergo a surface treatment. As discussed in Section 2.11, anodizing, a process whereby a surface is oxidized, increases corrosion resistance and wear resistance. It is usually applied to protect aluminum alloys.
Introduction to Corrosion
Published in S.K. Dhawan, Hema Bhandari, Gazala Ruhi, Brij Mohan Singh Bisht, Pradeep Sambyal, Corrosion Preventive Materials and Corrosion Testing, 2020
S.K. Dhawan, Hema Bhandari, Gazala Ruhi, Brij Mohan Singh Bisht, Pradeep Sambyal
Anodic coatings can be formed in sulfuric acid, chromic acid, phosphoric acid or oxalic acid solutions. Chromic acid anodizing is widely used with 7000 series alloys to improve corrosion resistance and paint adhesion, and unsealed coatings provide a good base for structural adhesives. The thickness of aluminum oxide coating produced by anodizing varies from 2 mm to 25 mm. In industry hard coat anodizing takes place where anodization is carried out in H2SO4 medium because it provides durable coating and resistance to abrasion; and corrosion resistance is needed and bulk anodizing for carrying out anodization on small, irregular shaped articles, which are processed in perforated aluminum is performed. Anodizing processes are also carried out on titanium and magnesium alloys. The process produces a smooth coating with a uniform texture and appearance, and a uniform blue to violet color.
Selective removal of aluminum, nickel and chromium ions by polymeric resins and natural zeolite from anodic plating wastewater
Published in International Journal of Environmental Health Research, 2021
The factory is among the four largest aluminum profile production facilities in Kayseri. Aluminum profiles, semi-finished products used in many industries, are produced by extrusion process from aluminum billets in a length of 13 m. The annual volume of aluminum profile production of the factory is 11,520 tons and of which 7500 tons are derived from the anodic oxidation process. In the plant, anodizing plating process, also known as anodic oxidation or eloxal, comprises of cleaning, caustic etching, acid neutralization, aluminum anodizing, coloring, fixing and drying processes. Aluminum anodizing is an electrochemical process that involves submerging aluminum profile in a tank filled with acidic electrolytic solution while passing electrical current between anode and cathode. A layer of aluminum oxide is settled down on aluminum profile and the desired color (bronze-black) is adjusted by changing the duration of application of nickel and chromium solutions (Ates and Uzal 2018). Wastewater sources throughout aluminum profile production are presented in the flow chart in Figure 1.
The effect of adding lanthanum nitrate on anodizing process of zirconium-niobium alloy
Published in Inorganic and Nano-Metal Chemistry, 2020
Mohsen Asadi Asadabad, Ramin Shoja Gharabagh
One of the special properties of zirconium alloys is excellent corrosion resistance, which results in their widespread use in fission nuclear reactors.[1] At room temperature an oxide film with a thickness about 2–5 nm is formed on the surface of zirconium alloys.[2,3] Although, the oxide film improves corrosion resistance, at high temperatures the reaction of zirconium oxide with steam results in problems such as release of hydrogen gas. The penetration of this gas into the fuel rod and the formation of hydride phases will have a destructive effect on the performance of the fuel complex. Increasing the thickness of the oxide layer can improve the corrosion resistance and delay the formation of the hydride phase.[4] Anodizing is an electrochemical process that thickens oxide layers formed on active metals such as aluminum, zirconium, and tantalum.
An Investigation Into the Synergistic Effect of CAPVD Cr/CrN Nanolayered Coating Deposition and Hard-Anodizing Methods on Fretting Fatigue Life of 7075-T6 Aluminum Alloy
Published in Tribology Transactions, 2023
G. H. Majzoobi, H. Asgaribakhtiari, H. Elmkhah
Anodizing is categorized as a surface engineering method that improves surface hardness and corrosion resistance of aluminum. In this process, a columnar arrangement of self-ordered tubular pores, termed anodic aluminum oxide, is perpendicularly grown on the Al substrate (alumina). This low-cost technique provides a porous thin film deposition on Al-based alloys even if the body is of very large dimensions (21). Hard anodizing is a specific type of anodizing where a thick layer of oxide is formed on an Al substrate, often more than 50 µm. The inherent characteristics and structural quality of the oxide layer are always influenced by the impurities and coating temperature. Higher purity of the Al alloy results in more appropriate oxide deposition (22).