Corrosion Resistance Tests Research Articles

Corrosion protection of sintered metal parts by coating deposition. Part II: Corrosion and electrochemical characterization

AbstractCoated sintered steel parts were subjected to corrosion resistance tests and electrochemical characterization. A wide range of industrially produced coatings, covering all the main proposed treatments, were analysed.Conventional corrosion tests were employed to compare corrosion resistance, whereas electrochemical test methods were used with the aim of giving a better understanding of the mechanisms which control corrosion processes and the corrosion rate. In particular, electrochemical impedance spectroscopy showed to be very helpful in allowing the monitoring of corrosion behaviour as a function of testing time, without introducing significant electrical perturbation on the examined system.The experimental results of this study showed that sintered steel protection by coating is possible if the process is very well controlled, however, defects in the coating can always be present due to the substrate porosity. With this fact in mind the use of sacrificial coatings is recommendable due to the possibility of a cathodic protection corresponding to coating defects.

Integrated sintering-coating of iron powder articles in metal-oxide mixture

Abstract A new method of production of wear- and corrosion-resistant articles and tools made of ferrous powders with chromium-based coatings is proposed. Wastes from the ferroalloy and artificial rubber industries were used as a mixture in the integrated sintering-coating process, allowing a considerable reduction in operational and technology-related expenses. Costs of production were also reduced since the mixture itself was made of industrial wastes and the sintering-coating process was performed without any protective atmosphere, i.e. without expensive heating equipment. A substantial contribution is the ample scope for producing intricate wear- and corrosion-resistant pieces of construction as well as different tools with intricate working surfaces. The results of corrosion resistance and mechanical tests carried out on powder tools and pieces treated according to the new technology have proved their high in-service abilities.

Black cobalt solar absorber coatings

A new electrolyte has been proposed for the deposition of black cobalt selective absorber coatings. These coatings are used in solar collectors for photothermal conversion of solar energy. We have studied the influence of electrolyte composition and operating parameters on the properties of the black cobalt coatings including optical (α, ϵ) and electcical properties. Thermal stability and corrosion resistance tests showed good durability of black cobalt selective coatings for high temperature applications.

Evaluation of the service life of protective coatings

A serious problem in predicting the service life of protective coatings is the absence of a reliable method for evaluating their corrosion resistance. At present the main criteria used to assess qualitative corrosion characteristics at high temperature are: (a) the weight index of corrosion (weight gain or weight loss); (b) the measured thickness of the remaining coating layer; (c) the number of heat cycles up to failure; (d) the length of time to full failure of the coating. None of these methods gives a very precise estimation and this leads to inaccuracy in predicting the service life of the articles in use. In order to evaluate the heat resistance of protective coatings under laboratory conditions a method has been developed as follows. (i) Corrosion resistance tests are carried out under conditions which closely simulate those found in actual operation. (ii) Coated specimens are selected periodically for testing: the concentrations of the elements in the coating, which give it its corrosion resistance, phase composition and structural state, are measured by the method of micro-X-ray spectral analysis. (iii) The results obtained are plotted on a graph. The protective properties of the coating are considered to be exhausted when the coating elements reach their concentrations in the substrate. This method has been tested on many types of metallic coatings, prepared by diffusion, plasma, electron beam, magnetron etc. processes, and was used to determine their service life. A U.S.S.R. State Specification has been formulated on the basis of these results.

Elimination of Intergranular Corrosion Susceptibility of a Sensitised 304 Steel by Subsequent Laser Surface Melting

The electrochemical behaviour of a sensitised 304 stainless steel which has subsequently undergone a fusion treatment of its surface with a continuous wave CO2 laser has been studied. The area directly affected by the fusion has a fine scale microstructure of austenite; the intercellular regions are interpreted as containing ferrite. The electrochemical corrosion resistance tests show that, following the laser treatment, the steel has regained its intergranular corrosion resistance properties.

Improving the quality and service properties of corrosion-resistant austenitic steels

A method of obtaining ultralow carbon high-nitrogen austenitic corrosion-resistant steels by solid-phase decarburization and alloying with nitrogen (SPDAN) was developed. The method makes it possible to attain low carbon content and a high nitrogen concentration. Experimental batches of thin-walled pipes made from several SPDAN-obtained steels (01Kh22AN10, 01Kh22N10AM2, 01Kh22N6AM2, 01Kh17N14AM2, 01Kh18AN11, and 08Kh18N10T) were comparatively subjected to tensile, corrosion resistance, and endurance tests. Results were analyzed and it was established that the SPDAN technology, devised for the production of thin-walled rolled stock of austenitic corrosion resistant steels, ensures a high level of strength and corrosive properties and also of endurance of finished products. Under conditions of intense intercrystalline corrosion the steels have to contain a small amount of molybdenum and not less than 22% Cr.

Methods of color anodizing the handles of dental rod instruments made of D1T aluminum alloy

1. The oxide films made chemically are friable and thin and have low wear resistance, and they do not withstand tests for corrosion and water resistance. This makes them unsuitable for protective and decorative finishing of medical instruments made of D1T aluminum alloy.

電気亜鉛めっき鋼板の耐食性に及ぼす浴中の金属イオンの影響

The effects of metal ions in plating bath such as Fe, Co, Ni, Cr, Mo, W, Mn, Cu, or Sn on the properties of electrogalvanized steel sheet were investigated by corrosion resistance and paint adhesion tests. The results are summarized as follows: (1) The range of adequate current density is broader in the bath containing Fe, Co, Ni or W ions, and narrower in the bath containing Cr, Sn or Cu ions. (2) The surface appearance of plated sheet is greatly affected by the sort and quantity of metal ion in the plating bath. Plated sheet has a tendency to show fine structure, as metal ions of Fe, Co or Ni in the bath increases. In the case of containing Mo or Cr ions in the bath, it shows massive structure. (3) The effect of additive element on the corrosion resistance of plated sheet is greatly affected by the corrosion circumstances. In salt spray test, for example, plated sheet obtained from the bath containing Sn or Cr ions has more excellent corrosion resistance than the conventional zinc plated sheet. On the other hand, in the outdoor exposure test and humidity test, it has less excellent corrosion resistance. Plated sheet obtained from the bath containing Co or Ni ions has more excellent corrosion resistance than the conventional zinc plated sheet in any test. (4) Plated sheet obtained from the bath containing Co, Mo, Cr, W or Fe ions has always more excellent corrosion resistance or more excellent paint adhesion after corrosion test than the conventional zinc plated sheet, though it is greatly affected by the sorts of paints and corrosion circumstances. Among these metal ions, Co ion has the greatest effect on the corrosion resistance.

防錆防食試験規格

防錆防食試験規格

Sorting Tests for Stress Corrosion Resistance of Cold Drawn Prestressing Tendon

Axially precracked.specimens are used in a 9 lot survey of SCC susceptibility of cold drawn prestressing tendons in alkaline solutions and at the free corrosion potential Considerable variation in susceptibility is noted under some conditions of test.While chlorides sensitise tendons to SCC, sulphides arefound to be innocuous at high pH.The parameter KISCC is determined for all tendons, but there appears to be insufficient variation to allow its use as an index of SCC susceptibility.

The Effect of Scan Rate on Pitting Potentials of High Performance Alloys in Acidic Chloride Solution

Abstract The effect of potential scan rate on the pitting potential determination of several high performance alloys in acidic chloride solution at 70 C was documented. Materials from several alloy classifications were examined including austenitic stainless steel, duplex stainless steel, 20-type stainless steel, and nickel base alloys. The functional relationship of pitting potential versus scan rate was dependent on the material studied. Results at intermediate and rapid scan rates were dependent on the material studied and on the experimental procedure. The response of the pitting potential of a given alloy to intermediate and rapid scan rates appears to be a function of the kinetics of passive film formation at the corrosion potential and at applied potentials. Therefore, the most promising accelerated electrochemical tests for localized corrosion resistance are the slow scan rate and constant potential pitting tests. Hastelloy alloy G was found to be resistant to pitting corrosion at all applied potentials in this environment. Additionally, the microstructural sites most susceptible to stable pit initiation were determined for the alloys investigated.

Tests of NASA ceramic thermal barrier coating for gas turbine engines

A two-layer thermal barrier coating system with a bond coating of nickel-chromium-aluminum-yttrium and a ceramic coating of yttria-stabilized zirconia was tested for corrosion protection, thermal protection and durability. Full-scale gas-turbine engine tests demonstrated that this coating eliminated burning, melting, and warping of uncoated parts. During cyclic corrosion resistance tests made in marine diesel fuel products of combustion in a burner rig, the ceramic cracked on some specimens. Metallographic examination showed no base metal deterioration.

ステンレス遠心鋳造管の諸特性について Ｉ

Tests of mechanical properties and corrosion resistance were made about centrifugal casting of austenite and ferrite-austenite stainless steels.The obtained results are as follows:(1) Tensile properties of centrifugal casting tube of SUS 304, SUS 316, SUS 316 L and SUS 329 J1 satisfy the requirement specifed in JIS G 4303 for bar. But 0.2% proof strength and tensile strength are low in comparison with actual results of bar.(2) Corrosion resistance of centrifugal casting tube of SUS316 and SUS 316 L for 5% H2SO4 almost satisfy the requirement specified in JIS G 4303 for bar.(3) 0.2% proof strength of DCS 1 shows a value two times higher then austenite stainless ateels, and tensile strength shows about 30kg/mm2 higher value than austenite stainless steels.And corrosion resistance of DCS 1 is superior to SUS 316 and SUS 316 L.

Effect of overheating on fatigue strength and other mechanical properties of carburized and uncarburized VAR 582 steel

Rotating cantilever fatigue tests were made on two vacuum-arc remelted casts of S82 (4%Ni) steel which had been preheated andforged to give a 25% reduction at 1060°, 1260°, 1300°, or 1340°C and then fully heat treated. Statistical analysis was applied to the results. Impact, tensile, fracture toughness, and stress corrosion resistance tests were carried out,. measurements of fatigue crack growth rate and a study offatigue crack initiation were also made. The tests showed that overheating, including fairly severe overheating, had no significant detrimental effect on fatigue properties, tensile strength, and fracture toughness but that it caused reductions in tensile ductility, impact toughness, and stress corrosion resistance.

Hard transparent dielectric coatings

Hard transparent corrosion-resistant dielectric coatings were investigated (a) for application to the direct protection of glass surfaces, (b) for application to the protection of thin film metallic window coatings used for reflection or transmission of solar radiation and (c) for use in codeposited metal-ceramic coatings. The dielectric coatings were Al 2O 3, SiO 2 and SiC in the thickness range 100–100 000 Å. The coatings were deposited under varying conditions of substrate temperature, gas composition, r.f. power and substrate preparation. The results of the following measurements on the dielectric coatings are presented: diamond pyramid hardness tests, optical reflectance and transmittance in the region 0.6–4.0 eV and corrosion resistance tests under cyclic conditions. The results showed a considerable improvement in the scratch resistance and hardness of glass by layering of hard dielectric coatings 2–5 μm thick.

Optical, mechanical and corrosion properties of metal-metal and metal-dielectric thin layered films

Optical, mechanical and corrosion properties have been studied on the following bilayer coatings: Cr-(67% Cu + 33% Zn), Ti-(67% Cu + 33% Zn), CuZn, AuCr, CrCu and CuNi. Both Crbrass and CrCu were studied with overlayers of SiO 2, with and without thin underlayers of Cr next to the SiO 2. Thus the systems CrCuCr, CrbrassSiO 2, brassCrSiO 2 and CrCuSiO 2 were also studied. These were compared with single layers of brass, Cr and Cu. Layered structures were deposited in both MRC diode and NRC triode sputtering systems. The triple-target r.f. diode system was used to sputter sequentially three different layer thicknesses. The thickness of the metallic layers was varied between 5 and 200 Å, while the SiO 2 thickness was kept constant at 670 Å. Results are presented for the optical reflectance and transmittance in the region 0.6–4.0 eV, the solar transmittance factors, DW (nm) and saturation index P. Hardness, scratch resistance and corrosion resistance tests under cyclic conditions were also made. It is shown that layering is a powerful technique for control of the optical, mechanical and corrosion resistance properties of the films.

Slag Portland cement for hydraulic structures operating under severe climatic conditions

Industrial slag portland cements produced from granular magnesia slags were studied concurrently with laboratory slag portland cements. All passed the autoclave tests for uniformity of volume change under a pressure of 20 kb/sq cm. There were virtually no deformations in 180-day specimens. Study results show that the strength of slag portland cement (SPC) increases steadily, and after 2 years exceeds the classical 28-day strength by a factor of 1.5-2.0. As compared with the conventional SPCs, the magnesia SPCs follow a high strength gain indicator from 28 to 360 days; this has a positive effect on massive concrete placed in hydraulic structures. As compared with th conventional SPCs the magnesia SPCs exhibit an even lower heat liberation, amounting to 34 and 45 cal/g after 3 and 7 days of hardening respectively. The quality of magnesia SPC was assessed from comparative corrosion-resistance tests, and the structural-engineering properties of the magnesia SPC were tested directly in concrete. The investigations confirm that magnesia-slag-based slag portland cements satisfy the technical specifications and that they are suitable for massive concrete in hydraulic structures.

A new system for conversion coatings

A new system for conversion coating and auto-catalytic plating has been developed based on a wet blast system. A comparison of the system with conventional processing is made showing the improvement in physical properties of the coatings and the reduction of effluent problems. A specific example of phosphating is given with reference to the chemical theory, crystalline structure and lubrication characteristics. Results of standard corrosion resistance, paint adhesion and lubrication tests are given.

Chemical Vapor Deposition of Silicate Glasses for Use with Silicon Devices: II . Film Properties

Chemical, dielectric, thermal, and optical properties of glass films synthesized by chemical vapor reactions from the hydrides are discussed. The binary borosilicate glasses deposited at low temperature from silane, diborane, and oxygen require a thermal densification to approach bulk glass properties. The rate of densification in the temperature range of 770°–800°C is very rapid but water vapor has an accelerating influence, allowing densification at reasonable rates at temperatures as low as 450°C. The thermal expansion match with silicon was sufficiently close to allow the crack‐free coating of wafers with 12µ of glass. Borosilicate films of 5µ thickness on silicon withstood severe thermal shock, temperature cycling, moisture penetration, and corrosion resistance tests. Densified borosilicate of typical compositions had a dielectric constant of 3.8–4.1 and a dissipation factor at 103 Hz of 0.10–0.15. The d‐c dielectric field strength sustained by MIS capacitors made from 1µ thick densified films measured before and after a 1‐yr exposure to room air, was . The properties of vapor‐deposited phosphosilicate glasses and of glasses containing the oxides of aluminum and zinc are briefly described.

ガス浸炭窒化処理鋼の耐食性について

Corrosion resistance test of carbon steel carbo-nitrided in the mixed gas of CO and NH3 at 550-850°C, were made in air, water, 10% NaCl, 1N NaOH, 0.1N H2SO4, HCl, and HNO3 solution without agitation, by observing the change of weight and surface condition.The result: -Carbo-nitrided steel, compared with plain carbon steel, had high resistivity in water, air, 10% NaCl, 1N NaOH solution, but low in mineral acids. That treated at 850°C showed poor result due to the precipitation of Fe3C in surface layer (e-phase) produced during carbo-nitriding.