Formation of Porous Anodic Films on Carbon Steels and Their Application to Corrosion Protection Composite Coatings Formed with Polypyrrole

Abstract

The growth behavior of nanoporous anodic films on carbon steel containing 0.213 mass% carbon has been examined. The films were grown by anodizing in an ethylene glycol (EG) electrolyte containing 0.1 mol dm −3 NH 4 F and 0.5 mol dm −3 H 2 O. The steel contains carbide precipitates with sizes in the range 50-800 nm. The anodic film formed on the carbide phase grew more slowly and was more chemically soluble during anodizing, resulting in submicrometer pits on the anodic film. The nanoporous morphology of the anodic films formed on an α-Fe matrix resembled those formed on iron. Heat treatment of the anodized specimens caused transformation of the chemically soluble fluoride-containing amorphous or poorly crystalline anodic films to crystalline oxide films containing α-Fe 2 O 3 and Fe 3 O 4 . Polypyrrole (PPy) was electropolymerized on the transformed surfaces to form a corrosion-protective composite coating. The resultant specimens coated with the composite coating showed improved durability compared to passivated steel with a PPy coating. Porous oxide films formed on aluminum and magnesium alloys by anodizing have been extensively studied for their ability to protect alloys from corrosion and wear; in addition, an anodizing process is of fundamental interest for the growth of self-ordered porous films. 1-3Recently, attention has been drawn to the formation of highly ordered nanoporous structures on aluminum, which are formed by the anodizing process, and their use in nanoscience and nanotechnology. 4 Furthermore, the formation of self-ordered nanoporous oxide films on a range of metals, including titanium, 5 zirconium, 6-8 niobium, 9 tantalum, 10 tungsten is also of interest. 11,12Iron is the most widely used metal. Recently, self-ordered nanostructured oxide films have been developed on iron using organic electrolytes containing fluoride and trace amounts of water. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] Depending upon the anodizing conditions, either nanoporous or nanotubular anodic films are formed on iron. 14,18,24,27 The as-formed anodic films are often amorphous and contain a relatively high concentration of fluoride species; however, such films are not chemically stable. Heat treatment of the anodized iron samples causes crystallization of the amorphous anodic film, forming mainly α-Fe 2 O 3 .16,17,21 α-Fe 2 O 3 is a promising material for solar-driven water splitting due to its low bandgap, low cost, abundance, and high chemical stability; consequently, nanostructured porous α-Fe 2 O 3 films formed by anodizing and subsequent heat-treatment have recently attracted much attention. 17,18 In addition to photocatalytic applications, porous anodic films on iron can be used to protect iron and steel from corrosion. Iron and steel alloys are often coated with paints to protect them from environmental corrosion. In addition, interest in the use of conducting polymer coatings has increased because they provide anodic protection due to their oxidizing ability; in addition, they act as a physical ba...

A Thermodynamic Approach for Selection of Anodizing Electrolytes in Aluminium‐Holmium System

“…A smoothening of the surface cannot be readily observable after anodizing due to the limited thickness of the anodic films (~10-15 nm) indicating that surface morphology is controlled by the texture of the original parent surface. [44,45] Nevertheless, low magnification SEM images (not shown here) clearly reveal the evidence of anodic film formation irrespective of the AlÀ Ho alloy composition and anodizing metals, which supports the idea of electrolyte selection based on thermodynamic considerations.…”

Chitosan-Based Architectures as an Effective Approach for the Removal of Some Toxic Species from Aqueous Media

“…T FTIR spectra of Cs-g-GA, Cs/GA/MBA, and Cs/GA/ECH are also displayed in Figure . The FTIR spectrum of Cs-g-GA reveals that the main peaks are shifted upfield or downfield from their original position due to the grafting process due to the interaction between the reacting groups which may include protonation, electron delocalization, and polarization. , For instance, the N–H and O–H stretching vibration peaks shifted to 3417 cm –1 , the CH 3 symmetric stretch shifted to 2993 cm –1 , the CO stretching vibration shifted to 1640 cm –1 , and the C–N stretching vibration shifted to 1470.7 cm –1 . , The appearance of the peak at 1513 cm –1 can be attributed to the grafting of GA onto the chitosan backbone. Also, the new sharp peak that emerged at 1640 cm –1 represents stretching vibrations of CN in Schiff’s base formed by the reaction of GA and CH.…”

“… 41 , 48 For instance, the N–H and O–H stretching vibration peaks shifted to 3417 cm –1 , the CH 3 symmetric stretch shifted to 2993 cm –1 , the C=O stretching vibration shifted to 1640 cm –1 , and the C–N stretching vibration shifted to 1470.7 cm –1 . 49 , 50 The appearance of the peak at 1513 cm –1 can be attributed to the grafting of GA onto the chitosan backbone. Also, the new sharp peak that emerged at 1640 cm –1 represents stretching vibrations of C=N in Schiff’s base formed by the reaction of GA and CH.…”

Highly Efficient Elimination of Pb+2 and Al+3 Metal Ions from Wastewater Using Graphene Oxide/3,5-Diaminobenzoic Acid Composites: Selective Removal of Pb2+ from Real Industrial Wastewater

“…A significant amount of work has gone into developing novel adsorbents for wastewater treatment in recent years. Due to their unique physical and chemical properties, carbon nanomaterials such as carbon nanotubes (CNTs) and graphene and its derivatives such as graphene oxide (GO) have drawn a lot of attention as potential adsorbent materials. − Graphene is a two-dimensional carbon-based nanomaterial made up of a monolayer of sp 2 -hybridized carbon atoms that are organized in a regular hexagonal pattern . Graphene comes in a variety of forms, including pristine graphene, GO, and reduced graphene oxide (RGO).…”