Showing papers in "Materials protection in 2015"

Corrosion Resistance of Anodic Oxidation Film on Aluminum Alloy

Abstract: Copper accelerated acetic acid salt spray corrosion tests of 6063 aluminum alloy and its anodic oxidation film were performed under the same conditions.The corrosion weight loss was measured with an electronic balance,while the corroded surface morphology and corrosion product composition were analyzed by scanning electron microscopy and energy dispersive spectrometry.Results showed that the anodic oxidation film on the Al alloy surface consisted of a barrier layer and a porous layer,and it was able to prevent the attack by Cl~- thereby greatly improving the corrosion resistance of the Al alloy.The corrosion of the anodic oxidation film initiated at the grain boundary,and the corroded pores were small in size and exhibited uniform size distribution.Moreover,the corrosion mass loss was proportional to time in power function mode,and the corrosion rate of the anodic oxidation film was dominated by a transitory increase in a certain period of time.With further extending time of corrosion,re-passivation occurred until the anodic oxidation film was totally corroded and broken.Besides,the corroded products mainly consisted of O,Al and P elements,accompanied by a small amount of Cl and S elements.

Properties of Nitride Coatings on Inside Wall of Reinforced Gun Barrel by Magnetron Sputtering

Abstract: TiAlN and CrAlN protective coatings were deposited on the surface of PCrNi3 Mo steel by magnetron sputtering methodThe composition and microstructure of the two coatings were characterized by confocal laser scanning microscope and X- ray diffractometerThe hardness and elastic modulus of the substrate material and the two coatings were measured by nano-indentationResults showed that the surface of CrAlN was smooth and dense and the roughness was smaller(R_M =0004 ~0006 μm)The surface roughness of TiAlN coating was larger(R_M= 0005 ~ 0021 μm)The main crystalline phases of CrAlN and TiAlN coatings were CrN and TiN respectively,and two phases preferrentially orientated along(110) and(200)respectivelyThe hardness and elastic modulus of CrAlN coating were 2039 GPa and 2888 GPa,and those of TiAlN coating were 1451 GPa and 2677 GPa,which were much higher than those of the subatrate material(557 GPa and 258 GPa)

Corrosion Behavior of Q235 Steel in Yingtan Acid Soil under DC Stray Current Effects

Abstract: The influence of DC stray current on corrosion behavior of Q235 steel in Yingtan acid soil with 30% and 40% moisture content was investigated by means of mass lossmeasurement,electrochemical impedance spectroscopy( EIS),microscope and X- ray diffraction analysis( XRD). Results showed that the corrosion behavior of Q235 steel was strongly dependent on the moisture content and DC stray current in acid soil. Local corrosion occurred on the surface of Q235 steel and EIS spectrum was an eccentric semicircle. Under the same moisture content in the acid soil,the EIS capacitive loop of Q235 steel was shrinked while the mass loss rate and maximum pit corrosion depth were increased with the increase of DC stray current. The corrosion rate of Q235 steel in the acid soil with 30% moisture was quicker than that in the acid soil with 40% moisture.

Structure and Corrosion Resistance of Hot Dip Galvanized Zn-Al-Mg-Ni-V Alloy Coating

Abstract: Zn-Al-Mg-Ni-V alloy coating was prepared by zinc alloy bath with less than 0. 5% other elements including Ni,V,Al and Mg. The structure and compositions of these coatings were analyzed by scanning electron microscopy( SEM) and energy dispersive spectrometer( EDS),and the corrosion resistance was evaluated by neutral salt spray test( NSST) and electrochemical analysis. Results showed that the corrosion resistance of Zn-Al-Mg-Ni-V alloy coating was much better than that of traditional pure zinc coating,while the main structure of coatings had no obvious change.

Effect of Nanoscale Alumina Additive on Microstructure as well as Corrosion Resistance and Wear Resistance of Electroplated Copper-Tin Alloy Coatings

Abstract: In view of the problems associated with electroplating of Cu-Sn alloy coating in pyrophosphate bath,nanoscale Al_2O_3 powder was introduced into the plating bath so as to improve the structure and properties of the as-plated alloy coating.The effect of the nanoscale Al_2O_3 additive on the microstructure as well as corrosion resistance and wear resistance of the Cu-Sn alloy coatings was investigated with an X-ray diffractometer,a scanning electron microscope,an energy dispersive spectrometer and an electrochemical test rig.Results showed that nano-Al_2O_3 additive could penetrate into the Cu-Sn alloy coatings during the directcurrent electroplating process,and it had a great influence on the microstructure and properties of the coatings.Namely,the as-plated Cu-Sn alloy coatings became more compact and uniform with increasing concentration of nano-Al_2O_3 additive,and their micro-hardness,corrosion resistance and wear resistance rose therewith.Particularly,the Cu-Sn alloy coating obtained under nano-Al_2O_3 concentration of 8 g/L,exhibited the highest micro-hardness as well as the best corrosion resistance and wear resistance.