Showing papers on "Salt spray test published in 2002"
TL;DR: In this article, the corrosion resistance properties of spray-and dip-coated 3-glycidoxypropyltrimethoxysilane (GLYMO) and TEOS Ormosil films have been investigated using salt spray analysis.
167 citations
TL;DR: In this paper, the use of new PANI formulations that are doped with phosphonic acids was introduced, and salt fog exposure tests point to phosphonic acid salts of PANI being more effective for corrosion protection than traditionally used sulfonic acid salt.
Abstract: Growing environmental concerns regarding the use of heavy metals in coating formulations have led to a new coating strategy using inherently conducting polymers (ICP), such as polyaniline (PANI), as a key component. The principal potential advantage offered by the ICP coating technology is toleration of pinholes and minor scratches. This paper introduces the use of new PANI formulations that are doped with phosphonic acids. Salt fog exposure tests point to phosphonic acid salts of PANI being more effective for corrosion protection than traditionally used sulfonic acid salts. Scanning reference electrode technology (SRET) data support the salt fog results in that the sulfonic acid dopants exhibited an increasing galvanic activity with time while the phosphonic acid dopants showed a decrease in activity with time, indicating passivation. A qualitative model is proposed which entails passivation of the metal surface through anodization of the metal by PANI and formation of an insoluble iron-dopant s...
154 citations
TL;DR: In this article, the corrosion behavior of a Cr III-based passivation treatment with and without a sealing treatment was studied, and the results indicated that the Cr III passivated coatings with sealing treatments have a corrosion resistance comparable with that of coatings having a Cr VI-based treatment without a sealant.
Abstract: Zinc coatings submitted to a Cr III-based passivation treatment, with and without a sealing treatment, were studied. For comparison, similar coatings with a Cr VI-based passivation treatment were also examined. The corrosion behaviour was studied by polarization resistance (Rp) measurements, anodic polarization and mainly by electrochemical impedance spectroscopy (EIS) in aerated 0.85 M NaCl solution. Salt spray tests and morphological observations on the coating surface were also performed. The results indicate that the Cr III passivated coatings with sealing treatments have a corrosion resistance comparable with that of coatings with a Cr VI passivation treatment without a sealant; therefore, they could be a less polluting alternative to the traditional chromated coatings.
77 citations
TL;DR: In this paper, primary aliphatic amines (diethylenetriamine, triethylenetetramine, tetraethylenepentamine) and super acids (CF3SO3H, HPF6) have been investigated as room temperature curing agents for hybrid organic-inorganic thin films.
62 citations
25 Sep 2002-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a study was made of the change in properties of 316L stainless steel depending on the type and the amount of added reinforcement, including intermetallics and carbides.
Abstract: A study was made of the change in properties of 316L stainless steel depending on the type and the amount of added reinforcement. The reinforcements used were Cr2Al, Cr2Ti, VC, SiC; and the amounts were 1.5 and 3 vol.%. All materials were manufactured by mixing the powders with 0.6 wt.% of wax, compacting at 700 MPa, and sintering at 1230 °C in a 75% H2–25% N2 atmosphere. The properties evaluated include sintering density, tensile strength, hardness, corrosion (salt spray test) and wear, and a microstructural study was also made. The intermetallics and carbides mostly improve corrosion properties without degrading mechanical properties.
44 citations
TL;DR: In this paper, the salt spray performance of nine different HT treatments on AA2024 (UNS 92024) as stand-alone conversion coatings and as a substrate for an epoxy primer were evaluated.
Abstract: Hydrotalcite (HT) conversion coatings are a possible alternative to chromate conversion coatings (CCC) for the pretreatment of aluminum aerospace alloys, but they must meet several criteria for acceptance. Relevant to acceptance are the abilities of these coatings to provide stand-alone corrosion protection, suitable adhesion with subsequent organic layers, and overall corrosion protection when used within a coating system. This study examines the salt spray performance of nine different HT treatments on AA2024 (UNS 92024) as stand-alone conversion coatings and as a substrate for an epoxy primer. In addition, the adhesion of epoxy to the HT and the corrosion characteristics of HT coatings as assessed by electrochemical impedance spectroscopy (EIS) were determined. Salt spray testing was performed under pertinent military specifications, and CCC was used as the benchmark. Two epoxy primers were evaluated: one with a chromate inhibitor (Class-C) and one with a nonchromate inhibitor (Class-N). The s...
43 citations
TL;DR: In this paper, the effect of Al addition on the corrosion performance of zinc-rich paints (ZRP) was investigated and the experimental results showed that the protective nature of ZRP altered from cathodic protection to barrier former as the Al content was increased beyond 20
34 citations
TL;DR: In this article, solvent-free siloxane-modified epoxy coatings were developed by the interpenetrating technique using epoxy resin as base (DGEBA, GY 250, Ciba-Geigy) and hydroxyl-terminated polydimethylsiloxane as modifier (commercially known as silicone) with γ-aminopropyltriethoxysilane as cross-linker, dibutyltindilaurate as catalyst, and 25% zinc powder as additive.
Abstract: Solvent-free siloxane-modified epoxy coatings were developed by the interpenetrating technique using epoxy resin as base (DGEBA, GY 250, Ciba-Geigy) and hydroxyl-terminated polydimethylsiloxane as modifier (commercially known as silicone) with γ-aminopropyltriethoxysilane as cross-linker, dibutyltindilaurate as catalyst, and 25% zinc powder as additive. Hexamethylenediamine (Aldrich) and polyamidoamine (HY 840, Ciba-Geigy) were used as curatives for the siliconized epoxy coatings containing 25% zinc powder. The corrosion-resistant behavior of these coating systems is assessed by electrochemical methods such as electrochemical potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopic methods. Based on the results obtained from the electrochemical potential measurements for epoxy and siliconized epoxy coating systems, few samples, namely AX4 and BX4, have been found to be the best corrosion-resistant coating systems, and they are used for potentiodynamic polarization measurements, electrochemical impedance, and salt-spray tests. The experimental results reveal that the siloxane (10%) modified epoxy coating system (AX4) with 25% zinc powder cured by hexamethylenediamine offers the maximum corrosion protection to the steel surface rather than the polyamidoamine-cured system (BX4). The better protective action offered by the coating system (AX4) is mainly imparted by the reaction of aliphatic amine hydrogens with oxirane groups of the epoxy resin, which gives coating films with a high cross-link density. The observation is further supported by a capacitive behavior in the Nyquist plot and no spreading of visible corrosion product in the salt-spray test.
26 citations
TL;DR: In this paper, the results proved the suitability of this technique to significantly enhance the mechanical properties and the surface finish of metal foams, and the corrosion behavior was tested performing a salt spray test.
Abstract: Aluminium foams produced via the PM-process are characterized by a moderate specific strength, a high surface roughness, and a poor wear behavior; to increase their mechanical properties and to improve the surface finish, wear and corrosion resistance; thermally sprayed coatings can be applied. The quality of the coating depends on the coating material, the chosen process, the preparation of the surface and spraying parameters. Aluminium alloys and iron based alloys for abrasive applications were deposited via electric arc spraying, ceramic coatings against wear were deposited by means of plasma spraying. Hard metallic coatings for severe abrasive applications were applied by high-velocity-oxyfuel spraying (HVOF). The results proved the suitability of this technique to significantly enhance the mechanical properties and the surface finish of metal foams. The specific strength and stiffness of the new composite materials outperform pure metal foams. The corrosion behavior was tested performing a salt spray test.
16 citations
TL;DR: In this article, the application of the electrochemical noise (EN) technique in the corrosion study on carbon steel in a salt-spray test is presented, and the resulting corrosion process is analyzed by the characteristics of the EN signal.
Abstract: This paper shows the application of the electrochemical noise (EN) technique in the corrosion study on carbon steel in a salt-spray test. Through this electrochemical technique the resulting corrosion process is analyzed by the characteristics of the EN signal. These results, achieved with a statistical analysis of the signal, which is related to the wire-on-screw test, show the electrochemical differences in uniform, pitting, and crevice processes.
8 citations
TL;DR: In this article, the corrosion behavior of AZ91D as-cast alloy was investigated form the viewpoint of the distribution aspect of precipitate (Mg17Al12) and the variation of Al concentration in the Mg-rich matrix.
Abstract: In the present study, the corrosion behavior of AZ91D as-cast alloy was investigated form the viewpoint of the distribution aspect of precipitate (Mg17Al12) and the variation of Al concentration in the Mg-rich matrix. The dendrite arm spacing (DAS) of an as-cast specimen was measured as a function of degree which describes the distribution aspect of the precipitate, and the salt spray test was conducted for various grain-sized specimens for 20 days. The dendrite arm spacing increased as the grain size increased to about 150 μm, but a constant value is indicated when the grain size exceeds that range. Although the relationship between the corrosion rate and grain size is of a nonlinear type, the linear trend between the corrosion rate and the dendrite arm spacing is maintained for the overall range of dendrite arm spacing. Since the precipitate in the as-cast alloy is discontinuously distributed, this linear relationship means that the variation of Al-solute concentration in the Mg-rich matrix has a more potent effect than the protective action of the precipitate on the corrosion behavior of an as-cast alloy.
TL;DR: In this article, the quality and durability of powder-coated hot-dip galvanized products have been investigated, and the use of delta-galvanized steel as a base for painting offers a number of advantages such as much greater hardness and improved paint adhesion.
Abstract: In this study, the quality and durability of powder-coated hot-dip galvanized products have been investigated. Standard steel coupons hot-dip galvanized in conventional and delta (i.e., high temperature) conditions were coated with powder paint systems or a high quality solvent-based system and then subjected to a wide range of test methods representing mild or highly aggressive exposure conditions. Additional variables in the project were the silicon content of the steel and the treatment prior to painting. The use of delta-galvanized steel as a base for painting offers a number of advantages such as much greater hardness and improved paint adhesion. Maximum corrosion protection is observed if the galvanized base is treated with chromate and sequentially powder coated with an epoxy primer followed by a polyester topcoat.
TL;DR: In this paper, a continuous belt inside an IBAD chamber is used for the preparation of multilayers on relatively large substrates (typically 20×30 cm 2 ), where the specific geometrical arrangement of two evaporators and a slit extraction source together with variation of the speed and direction of the moving belt provides the necessary parameters.
Abstract: Coil coating by using a continuous belt inside an IBAD chamber allows not only the coating of steel or polymer strips in the IBAD mode, but represents also a very flexible device for the preparation of multilayers on relatively large substrates (typically 20×30 cm 2 ). The specific geometrical arrangement of two evaporators and a slit extraction source together with variation of the speed and direction of the moving belt provides the necessary parameters. The possible variations range from single metal layers, alloy layers over gradient layers with increasing or decreasing content of one or both phases to multilayers consisting of 2 or more sublayers. The advantages of this technique are demonstrated by the preparation of Zn/Cr-, Zn/Ti- and Zn/Mn-coatings on steel. Mainly the improvement of the corrosion behaviour was studied in comparison with conventional electrogalvanized steels and alloys prepared by normal ‘static’ alloy deposition. The samples were analyzed by SEM/EDX measurements and an industrial-like salt spray test. It could be shown that most of the multilayer coatings had much better corrosion behaviour than the electrogalvanized reference samples.
TL;DR: In this paper, the main goal of the plasma anodisation is the substitution of the aqueous electrolyte by an oxygen plasma, and the corrosion resistance was proved in the salt spray test according to DIN 50021 SS.
Abstract: Sufficient corrosion'resistance of technical magnesium alloys is generally ensured by anodising the components in aqueous electrolytes. In the majority of cases these processes bear environmental risks due to the highly toxically electrolytes and are subjected to substantial legal regulations. Considering these facts the plasma anodisation seems to be a prospective method to obtain good corrosion resistance without using toxic substances. The main goal of the plasma anodisation is the substitution of the aqueous electrolyte by an oxygen plasma. The plasma anodised surfaces were well characterized and the corrosion resistance was proved in the salt spray test according to DIN 50021 SS. For the tests the magnesium die cast alloy AZ91 hp was used. The tests included plasma anodised, plasma anodised and PVD coated and only PVD coated specimens. After the salt spray test the surface of plasma anodised specimens showed sporadic filliform corrosion. The plasma anodised specimens showed superior corrosion behaviour in comparison to the only PVD- coated ones. The polished magnesium as well as the as casted samples showed more corrosion attack than the anodised specimens.
TL;DR: In this paper, four different organic systems, containing either vinyl acetate resins or epoxy resins were applied on steel pretreated specimens exposed to deionized and deaerated water taken from the installations of the Public Greek Electricity Company.
Abstract: Four different organic systems, containing either vinyl acetate resins or epoxy resins were applied on steel pretreated specimens exposed to deionized and deaerated water taken from the installations of the Public Greek Electricity Company. Electrochemical Impedance Spectroscopy, potentiodynamic polarization measurements, dielectric measurements and visual observations after salt spray test were performed for monitoring the changes of the organic systems characteristics at predetermined exposure time in the deionized – deaerated water. All four coating systems found providing protection on steel surfaces. The classification of their performance depends mainly on the composition of the primer, as well as, on the intrinsic characteristics of the other layers. Thus the system consisting of epoxy primer with zinc dust, epoxy high build layer and a two component epoxy paint with iron oxide is the one exhibiting the highest protection efficiency.
TL;DR: In this paper, a set of mild steel panels were exposed in a salt-spray chamber for 720 hours and another set of panels at Chennai Port for 18 months, and the measurements were conducted in a 0.5M sodium chloride solution.
Abstract: Wire-brushed mild steel panels were coated with three coating systems: vinyl, epoxy-urethane and polyurethane systems. A set of panels was exposed in a salt-spray chamber for 720 hours and another set of panels at Chennai Port for 18 months. The panels were then removed from the site, and salt-spray chamber and AC impedance measurements were conducted in a 0.5M sodium chloride solution. The photographs of the panels exposed in the salt-spray chamber and at Chennai Port indicated that all the panels in the Port site had higher corrosion spots and blisters than that in the salt-spray chamber. The AC impedance observations of both sets of panels indicated that the resistance offered by the vinyl and epoxy-urethane systems were in the order of 109ohmcm2, whereas in the polyurethane system, the resistance was in the order of 105 to 104ohmcm2. Thus better correlations were obtained between the AC impedance and salt-spray tests, and with field exposure data for the epoxy-urethane and vinyl systems, but a slight variation of this correlation was observed in the case of the polyurethane system. Thus it was concluded that vinyl and epoxy-urethane coating systems should be used as maintenance coating systems for mild steel surfaces for the corrosive atmosphere prevailing in the Chennai Port environment.
Journal Article•
TL;DR: In this paper, hot dipping using molten zinc has been examined as an alternative approach to metal coating for corrosion protection of sintered iron-base parts, the quality and corrosion protection offered by the coating was evaluated as a function of part shape and microstructure, and from salt spray and potentiodynamic polarization tests.
Abstract: Sintered ferrous powder metal parts and components exhibit inferior corrosion resistance compared to wrought materials because of the presence of open porosity. Zinc coatings applied by electrodeposition or electroless deposition offer corrosion protection. In the present study, hot dipping using molten zinc has been examined as an alternative approach to metal coating for corrosion protection of sintered iron-base parts, The quality and corrosion protection offered by the coating was evaluated as a function of part shape and microstructure, and from salt spray and potentiodynamic polarization tests, and the determination of tolerances. Hot dipping was shown to result in thicker coatings than in electro-depostion with improved corrosion protection; the zinc coating seals open pores and covers areas which are difficult to reach with other deposition techiques. The change in tolerance is higher for hot dipping than for electrodeposition. It is concluded that hot dipping is a rapid, low cost coating process for corrosion protection that does not require pretreatment.
TL;DR: In spite of its shortcomings, the salt spray test is universally used to characterize the corrosion resistance of zinc based coatings as discussed by the authors, and a working group has tried to improve its reliability by the introduction of a new calibration method of the equipment.
Abstract: In spite of its shortcomings, the salt spray test is universally used to characterize the corrosion resistance of zinc based coatings. A working group has tried to improve its reliability by the introduction of a new calibration method of the equipment. The outcome of the work is the definition of a new testing procedure, presently adopted in France for the control of coated products delivered to the automobile industry.
TL;DR: In this article, the results of short term corrosion tests (salt spray test, Kesternich test) with sprayed ZnAl-coatings with an aluminium content of 2 to 50 M.-%.
Abstract: By alloying aluminium to zinc the corrosion resistance can be increased in a multiplicity of media. Thermally sprayed ZnAl 15-coatings show a higher corrosion resistance than thermally sprayed zinc- or hot dip galvanized coatings. This paper presents the results of short term corrosion tests (salt spray test, Kesternich test) with sprayed ZnAl-coatings with an aluminium content of 2 to 50 M.-%. The investigations verify very clearly the influence of aluminium on the corrosion behaviour. Depending on the aluminium content the corrosion resistance shows a maximium with a medium content of about 15 or 22 M.-%.
TL;DR: In this article, the zinc dust priming coat was applied to a 1-pack polyurethane and an epoxy/2-pack PPG system on a hand-cleaned steel substrate.
Abstract: The protective mechanisms of paint systems of a 1-pack polyurethane- and an epoxy/2-pack polyurethane-coating system with zinc dust priming coats were investigated on blast-cleaned and on hand-cleaned steel substrates. The coated panels were exposed to the salt spray test and to a cyclic alternating test (VDA 621-415). The protective effect was assessed in determining adhesion, undermining at scratches, water uptake and the corrosion potential. On blast cleaned steel substrates the adhesion of the investigated coating systems was not influenced by water uptake of the coatings. Scratches are especially cathodically protected. On hand-cleaned steel surfaces the rust layer between steel substrate and coating can participate in the corrosion process with rust reduction as cathodic partial reaction. The change of rust morphology is the reason for the loss of adhesion of coating. At scratches rust reduction takes also place at the edge of the defect which is independent from pigments of the base coating.
TL;DR: In this article, the residual stress of crack-free Cr layers deposited by pulse-current electrolysis was evaluated by the X-ray diffraction method, and various residual stresses were measured.
Abstract: Several crack-free Cr plating processes using pulse-current electrolysis have been proposed for improving corrosion resistance. However, industrial applications of crack-free Cr platings are very few since these Cr layers are subjected to tensile residual stress and easily form macrocracks after plating operations, particularly at temperatures higher than 373K. The residual stress of crack-free Cr layers deposited by pulse-current electrolysis was evaluated by the X-ray diffraction method. With changing pulse conditions, various residual stresses were measured. The specimen in which initial compressive residual stress of the Cr layer exceeded -150MPa did not form macrocracks after holding at 473K for 2h, and showed a high corrosion resistance without rusting even after a 700h neutral salt spray test (NSST). The amount of change in the residual stress as a result of heat treatment correlated with the integral breadth of the diffraction profile, and became smaller and more stable with heat treatment as the integral breadth became narrower.