Showing papers on "Salt spray test published in 1998"

Conductive organic coatings

Abstract: The invention relates to conductive, weldable anti-corrosion compositions with a base consisting of (blocked) polyurethane resins, epoxide resins and nitrogenous resins and conductive fillers The inventive compositions are suitable for coating metal surfaces, especially steel sheets, using the coil-coating technique, and are characterised by a low burning-in temperature, by a significant reduction of white rust on galvanised sheet steel in the salt spray test and in that the organic coating adheres better to the metallic substrate These coatings also provide adequate protection against corrosion even with low chrome plating, preferably also with Cr-free pre-processing techniques Sheets coated in this way can be spot-welded using any conventional technique

A Correlation Between Salt Spray and Electrochemical Impedance Spectroscopy Test Results for Conversion-Coated Aluminum Alloys

Abstract: The corrosion resistance of 33 inorganic conversion coatings applied to five aluminum alloys was tested by salt spray exposure and electrochemical impedance spectroscopy (EIS). Results were evaluated to determine if a relationship existed. Individual salt spray test panels, with an area of 30 in. (194 cm2), were inspected visually at regular intervals up to 168 h of exposure. At each inspection interval, panels were assigned a pass rank if 5 pits were observed. EIS data were analyzed using a simple equivalent circuit which yielded a coating resistance (Rc), which was used as a figure of merit to assess coating performance. Examination of the data showed both tests could be sensitive discriminators of corrosion protection, but that EIS was more discriminating in the extremes of coating performance. Analysis showed the probability of achieving a passing salt spray result increased as Rc increased. In the regimes where both tests were sensitive, regression...

Electrochemical Impedance Spectroscopy and Fourier Transform Infrared Spectroscopy of Natural and Accelerated Weathering of Organic Coatings

Abstract: Effects of the natural degradation of protective organic coatings after exposure for some years in an industrial atmosphere (Turin, Italy) and the consequences of artificial weathering in an ultraviolet (UV) chamber (ASTM G 53) and salt spray test chamber (ASTM B 117) were compared using electrochemical, infrared, and calorimetric techniques. The comparison showed some differences between natural and accelerated weathering in the degradation mechanisms and provided information regarding future developments for new testing procedures.

Improvement of protective coating on Nd-Fe-B magnet by pulse nickel plating

Abstract: Sintered Nd–Fe–B magnets were coated by pulse nickel plating at different plating conditions. Optimal pulse plating condition was established (average current density=1 A/dm2, peak current density=6 A/dm2 with Ton:Toff=1:2). In order to make a comparison, magnets with similar nickel coating thickness plated by dc were also prepared. The corrosion resistance of the coated magnets was evaluated by (i) Normal Salt Spray Test (5% NaCl, 35 °C) and (ii) potentiodynamic polarization measurement (3.5% NaCl solution). It was found that the corrosion resistance of the pulse nickel plated magnet was significantly improved as compared with that of the conventional dc plated ones, with negligible deterioration in magnetism. The microstructure of the coating was examined by optical microscopy and scanning electron microscopy. It was found that the porosity was much lower, and the grains much finer in the pulse-plated layer as compared with the dc plated ones.

The influence of the method of application of the paint on the corrosion of the substrate as assessed by ASTM and electrochemical method

Abstract: AC together with DC and standardized procedures have considerable value in assessing the protective ability of a paint film by scientific studies of anticorrosion problems. Knowledge about the changes in permeability, conductivity and adhesion properties of coatings when exposed to aggressive environments is important, not only because it indicates how the coating may behave in practice, but also because it gives an insight into its protective properties in prevention of corrosion of the metal substrate. From the values of corrosion potential, ionic and charge transfer resistance with immersion time, the alkyd paint applied by means of four different methods showed relatively good protective properties in the order Sy>R ≅ Sn but very poor ones for B panel. On the other hand, when submitted to the salt spray cabinet test, all the steel panels coated with unscribed alkyd films have shown high resistance to the strongly aggressive medium. Likewise, the cross scribed panels show only corrosion at and close to the cross-scribing. Taking into account the overall results, the most effective application method was spraying followed by roller coating, spinning and lastly brushing. Further work needs to be done to confirm some of the assumptions made here.

Corrosion characteristics of pure magnesium refined by vacuum distillation.

Abstract: Relation between the amount of refined pure magnesium, impurities in the refined magnesium and purification time has been investigated for vacuum distilled magnesium alloys AM100A and AM60B. Corrosion characteristics of pure magnesium which was refined and then remelted in a vacuum high frequency induction furnace were investigated by means of a salt spray test and an electrochemical method. The extent of purification, defined by the quantity ratio of refined magnesium to alloy used increases linearly with increasing purification time, though purification rate is higher in alloy AM100A than in alloy AM60B. Zinc content in the refined magnesium decreases with purification time. The corrosion loss of the remelted pure magnesium in salt spray test, is as low as that of high purity commercial magnesium alloys. Both the amount of impurities and the current density of cathodic part of polarization curve are greater in the commercially pure magnesium than in the refined pure magnesium.

Rapid Electrochemical Corrosion Testing of Chemically Passivated Aluminum Alloys

Abstract: The corrosion resistance of 33 different conversion coatings applied to five different aluminum alloys was tested by salt spray exposure and electrochemical impedance spectroscopy (EIS). Results derived from the two tests were evaluated to determine if a relationship existed. Individual salt spray test panels, with an area of 30 in.{sup 2}, were visually inspected at regular intervals up to 168 hours of exposure. At each inspection interval, panels were assigned a pass rank if less than 5 pits were observed, or fail rank if more than 5 pits were observed. EIS data were analyzed using a simple equivalent circuit which yielded a ``coating resistance,`` R{sub c} which was used as a figure of merit to assess coating performance. Examination of the data showed that both tests could be sensitive discriminators of corrosion protection, but that EIS was more discriminating in the extremes of coating performance. Analysis showed that the probability of achieving a passing salt spray result increased as R{sub 2} increased. In the regimes where both tests were sensitive, regression analysis showed that linear relationships could be constructed between the log of R{sub c} and the probability of a coating meeting the pass/fail criterion in salt spray. Based onmore » these relationships, threshold R{sub c} values have been proposed to define the minimum value for which a given coating can be expected to attain a passing result in a 168 hour salt spray test.« less

Corrosion behaviours of the epsilon phase/complex oxide double-layer on mild steel

Abstract: This paper deals with the corrosion characteristics of the double-layer consisting of the epsilon phase and the complex oxide. The tests show that the double-layer protects the steel substrate effectively. The double-layer is superior in corrosion resistance to the single e-phase layer by three to four times, and to the e-phase / magnetite (Fe 3 O 4 ) layer by two times. The corrosion mechanisms have been investigated and discussed by means of metallography.

Surface treated steel strip

Abstract: PROBLEM TO BE SOLVED: To effectively prevent and reduce the generation of rust of a sheet cutting shear plane caused at the time of storage and transport by coating designated percentage of the area of a steel base metal in a bar cutting shear plane with a plating layer wrapped round it at the time of shearing. SOLUTION: The board thickness of a surface treated steel strip is 0.2-2.0mm. 40-90% of a shear plane of a steel base metal is coated with a wrapped-round plating layer. Also in the case where the coating percentage exceeds 90%, it is possible to obtain an excellent salt spray test result. In the case of setting the coating percentage 90% or more, the clearance is set smaller and the total groove depth is increased. If 40% or more of the shear plane of the steel base material is coated with a plating layer, even if a salt spray test is made about thirty days, rust will not be generated, so that rust is not generated during storage and transport.