Development of Nanostructure based Corrosion- Barrier Coatings on Steel for Transmutation Applications: Quaterly Report (original) (raw)
Related papers
Diffusion coatings for high temperature corrosion protection of 9–12%Cr steels
Corrosion Engineering Science and Technology, 2005
Steels containing 9-12%Cr are of great interest for application as heat-exchanger tubes in power stations. Indeed they possess a high thermal conductivity and favourable mechanical properties at temperatures up to 650uC. However, from a mechanical point of view, even though conventional ferritic-martensitic 9-12%Cr steels are designed for service temperatures up to 650uC, their use at such high temperatures is rather limited in corrosive environments. One solution may be to protect these steels by suitable corrosion-resistant coatings. Pack cementation is one of the easiest and cheapest coating processes for high temperature applications. However, for ferritic-martensitic steels, the maximum coating temperature is limited to 650uC. Above this limit, the decomposition of martensite would be accelerated, to the detriment of the mechanical properties of the material. The objective of the present work was to use pack cementation to coat the 9%Cr steel P91 and the 12%Cr steel HCM12A without modifying their microstructure. Therefore, the coating process was either carried out at 650uC or combined with the heat treatment of the ferritic-martensitic steel. As a result of the low coating temperature, aluminide coatings were developed first. Later, a two-step CrzAl coating was obtained. The corrosion resistance of the coatings developed was tested at 650uC for 1000 h in a simulated coal firing atmosphere composed of: 14%CO 2 , 10%H 2 O, 1%O 2 , 0. 1%SO 2 , 0. 01%HCl (bal. N 2). The coated samples showed better resistance to corrosion than the uncoated materials. The investigations were then extended to include aluminide coatings applied by fluidised bed chemical vapour deposition (FBCVD) on 9-12%Cr steels. Eventually, the corrosion resistance was compared with that of coated and uncoated austenitic steels as well as the nickel-based alloy IN617.
HOT CORROSION BEHAVIOUR OF Cr MODIFIED ALUMINIDE COATINGS DEPOSITED ON
Hot corrosion behaviours of diffusion and Cr modified diffusion coatings are compared in the paper. Diffusion aluminide coatings are applied on nickel superalloy, creating a protective heat-activated Al 2 O 3 layer, which acts as a protective barrier. The key to the success of Cr relating to elimination of corrosion is hidden in the fact that Cr 2 O 3 can be dissolved to form several valence states and moreover, the solubility in basic melt depends on oxygen pressure. The result is a positive solubility gradient. Since Cr in the modified aluminide coatings is present in both, precipitates and Ni solid solution, it should prevent martensitic transformation of nickel rich β -NiAl. Whereas Cr increases Al activity in Ni-Al system, greater Al depletion should be tolerated before NiO forming on the surface. Hot corrosion is the accelerated oxidation of a material at elevated temperature induced by a thin film of fused salt deposit. Superalloys samples were coated by help of the method outofpack. Corrosive environment was created using tablets Na 2 SO 4 at temperature 920 °C at Silesian University of Technology in Katowice, Poland. Hitachi SEM with EDS microanalysis was used for analysis of surfaces and cross -sections of the samples.
Corrosion Protection of Steel Using Nano Ceramic Particles Coating
In this work, three nanoparticles were used to apply seven different coatings on carbon steel using atomization method (cold spraying) by airbrush to achieve three types of coating. The first is single coatings, including Al2O3, SiC and ZrO2 coatings. The second is binary coatings, including Al2O3 - SiC, Al2O3 - ZrO2 and SiC- ZrO2 coatings. While, the third is Al2O3 - SiC - ZrO2 coating. The characterization of coated surfaces were investigated by AFM and SEM. All these inspections indicated the deposition of nanoparticles on carbon steel surface. The thickness of coated layers were calculated using gravimetric method, while the particle size and roughness were measured from the analysis of atomic force microscopy. The thickness of nanoparticle coatings are 6.22160 μm, 0.0781 μm, 1.5504 μm, 0.5145 μm, 3.469 μm, 1.3680 μm , 2.2152 μm for Al2O3, SiC, ZrO2, Al2O3 - SiC, Al2O3 - ZrO2, SiC- ZrO2, Al2O3 - SiC - ZrO2 respectively. While, the roughness values are 7.0nm, 26.1nm, 5.44nm, 6.86nm, 8.11nm, 6.64nm, 25.2nm for Al2O3, SiC, ZrO2, Al2O3 - SiC, Al2O3 - ZrO2, SiC- ZrO2, Al2O3 - SiC - ZrO2 respectively. Corrosion test was achieved to estimate the corrosion resistance, protection efficiency and porosity percentage. The corrosion potential shifted to more positive value for coated surfaces, and the corrosion current density became lower for coated surfaces. The corrosion rate was decreased.
Corrosion properties of steel protected by nanometre-thick oxide coatings
Corrosion Science, 2014
A comprehensive study of the corrosion properties of low alloy steel protected by 40-50 nm aluminium and tantalum mixed oxide coatings grown by atomic layer deposition is reported. Electrochemical and surface analysis was performed to address the effect of substrate surface finish and whether an oxide mixture or nanolaminate was used. There was no dissolution or breakdown for nanolaminate alumina/ tantala stacks in acidic NaCl solution. Localised corrosion (pitting) took place when defects exposing the substrate pre-existed in the coating. Substrate pre-treatment by brushing and H 2-Ar plasma was instrumental to block or slow down pit initiation by reducing the defect dimensions.
Formation of Surface Corrosion-Resistant Nanocrystalline Structures on Steel
Nanoscale Research Letters, 2016
Engineering materials with nanocrystalline structure could be exploited under simultaneous action of mechanical loading and corrosion environments; therefore, their corrosion resistance is important. Surface nanocrystalline structure was generated on middle carbon steels by severe plastic deformation using the method of mechanical pulse friction treatment. This treatment additionally includes high temperature phase transformation and alloying. Using a complex of the corrosive, electrochemical and physical investigations, it was established that nanocrystalline structures can be characterized by lower or increased corrosion resistance in comparison with the reference material. It is caused by the action of two confronting factors: arising energy level and anticorrosive alloying of the surface layer.
Corrosion Protection Study of Carbon Steel and 316 Stainless Steel Alloys Coated by Nanoparticles
The Corrosion protection effectiveness of Alimina(Al2O3,50nm)and Zinc oxide (ZnO,30nm) nanoparticales were studied on carbon steel and 316 stainless steel alloys in saline water (3.5%NaCl)at four temperatures: (20,30,40,50 OC)using three electrodes potentiostat. An average corrosion protection efficiencies of 65 %and 80% was achieved using Al2O3 NP's on carbon steel and stainless steel samples respectively, and it seems that no effect of rising temperature on the performances of the coated layers. While ZnO NP'S showed protection efficiency around 65% for the two alloys and little effected by temperature rising on the performanes of the coated layers. The morphology of the coated spesiemses was examined by Atomic force microscope.
Coatings
The improvement of the surface properties of ferrous metallic materials has become a crucial criterion for advanced engineering applications. The interfacial microstructure and corrosion behaviour of mild steel coated with alumina nanoparticles doped in tin composite using the direct tinning technique were investigated. A coating layer of tin composite containing different loads of Al2O3 nanoparticles (0.25 wt.%, 0.50 wt.%, 1.00 wt.% and 1.5 wt.%) was prepared and directly deposited on a mild steel substrate. This type of a direct tinning process is considered to be a simple and low-cost route for protecting metallic materials from corrosion. It was found that the thickness of both the composite layer and Fe-Sn intermetallic layer at the coated interfaces was highly affected by the presence of alumina nanoparticles that effectively inhibit the diffusion of Sn atoms into the Fe substrate. For the samples coated with lower content of alumina nanoparticles (0.25 wt.% and 0.50 wt.%), th...
Corrosion, 2014
Synthesized boehmite (AlO[OH]) sol was deposited on 9Cr-1Mo ferritic steel substrates using a dip coating technique. The coated substrates were heat-treated at 300°C to obtain a precursor-free alumina coating. Atomic force microscopy (AFM) analysis of the coated surfaces confirmed the presence of nano-sized alumina particles (8 nm to 12 nm) in the coating. The alumina-coated and uncoated samples were subjected to a hot corrosion test in lithium chloride-sodium chloride (LiCl-NaCl) and sodium sulfate-potassium sulfate (Na2SO4-K2SO4) salt mixtures separately at 650°C and 850°C, respectively. Oxidation kinetics study has indicated a significant improvement in the hot corrosion resistances of the coated substrates. Microstructural examinations of the oxidized substrates have revealed the presence of comparatively compact and less porous oxide scale at the coated specimens, whereas relatively very thick scale filled with cracks and voids were noticed on the uncoated oxidized specimens.
Corrosion Protection of Steel with Oxide Nanolaminates Grown by Atomic Layer Deposition
Journal of The Electrochemical Society, 2011
Atomic layer deposited (ALD) aluminum and tantalum oxide (Al 2 O 3 and Ta 2 O 5 ) and their nanolaminates were applied as corrosion protection coatings on AISI 52100 steel. The aim was to combine the good sealing properties of Al 2 O 3 with the chemical stability of Ta 2 O 5 and to optimize the coating architecture in order to obtain the best possible long-term durability. Coating composition and morphology were studied with time-of-flight elastic recoil detection analysis (ToF-ERDA), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and field emission scanning electron microscopy (FESEM) and energy dispersive x-ray spectrometry (EDS). Electrochemical properties were studied with voltammetry and electrochemical impedance spectroscopy (EIS), and corrosion durability with neutral salt spray (NSS) testing. The coatings were observed to be conformal and uniform over rough surfaces, and contained some carbon and hydrogen as impurities. The electrochemical results showed that the Al 2 O 3 coating had superior sealing properties compared to the Ta 2 O 5 coating, and nanolaminates had properties in between those of Al 2 O 3 and Ta 2 O 5 . However, in the NSS test the laminate-coated samples survived the best demonstrating long-term durability. Analysis of the laminate structure showed that for 40 and 80 nm laminates the best protection was achieved with 10 and 20 nm layers, respectively.