Salt Fog Test Research Articles

Performance evaluation of modified multi gap arrester

The distribution network due to lightning strikes. There are several types of arresters to be developed. A modified multi gap arrester was tested to know its performance. The method used to determine its performance was done by comparing it with metal oxide type arresters through a series of laboratory tests. The testing consists of impulse test, salt fog test, and follow current interrupting test. The arrester performance related to residual voltage, breakdown voltage, and the ability to interrupt follow current were obtained through the tests. By knowing the performance of modified multi gap arrester, it can be used as a consideration in applying this technology related to the insulation stress of protected equipment and the potential for follow current phenomenon.

PROTECTION OF ALUMINUM 6061 USED IN WATER VEHICLES FROM FLOUR FROM SALT CORROSION BY COATING

Aim: Every country in the world develops defense strategies in order to protect their borders and to be cautious against attacks from outside, according to their geographical locations. They use underwater and surface vehicles to meet the defense needs of countries that have coasts on seas or oceans. These vehicles need to be light in order to have low fuel consumption and high mobility. Method: Aluminum and aluminum alloy materials are generally used in these vehicles in order to meet these requirements and also to have high strength. In these vehicles, which are in motion in water, corrosion and abrasions occur on the surfaces due to high pressure and friction. Coating methods are applied to minimize these corrosions and abrasions. The selection of aluminum to be applied to these coating methods and the heat treatments to be applied to aluminum materials before coating will be evaluated. In this study, by giving examples of coating types, studies will be carried out on how much the formation of corrosion on aluminum surfaces reduces or prevents. Salt fog test will be applied in order to determine the decrease in the amount of corrosion formation. Salt fog testing will be performed in accordance with the MIL-STD-810G standard. Samples will be prepared for the studies to be carried out on the aluminum 6061 alloys. These samples will be aged by T6 heat treatment. After the aging process, for anodized coating types such as type 1 class 3, type 2 class 1 type 2 class 2 type 3 class 1 type 3 class 2 from anodic anodized coating types, each sample will be in the salt cabinet for 50 hours each turn to see the difference clearly. will be subjected to the fog test. After every 50 hours, the sample will be left to dry for 50 hours. After 50 hours of drying time, these samples, which were subjected to salt fog test, will be compared with each other before the test under normal conditions and after drying after the test.Results: In this study, it has been tried to determine how the aluminum 6061 alloy, which is one of the most preferred materials for underwater and above-water vehicles, behaves against corrosion after T6 heat treatment and the coating types that should be applied in order to maximize its resistance against this corrosion. Conclusion: When the images taken from the optical microscope were compared, it was observed that the type 3 class 1 type was more durable than the other coating types.

Corrosion Resistance of Clay Modified Resole and Novolac Phenolic Coatings

In this study corrosion resistance and adhesion properties of two types of phenolic coatings, novolac and resol, have been investigated. Phenolic coatings containing clay particles were prepared and the effect of clay content on the corrosion protection performance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS), DC polarization and salt fog tests. On the other hand, adhesion and toughness characterization of prepared phenolic coatings was measured using pull off and cupping tests, respectively. Results indicated that adding of clay particles, improves the corrosion protection performance both of both types of phenolic coatings. Novolac phenolic coating containing 3 wt % of clay showed higher corrosion resistance than the others. Also, test results showed that the flexibility and adhesion of resol coating was more than that of the novolac coating.

Chamber Protection of Copper from Atmospheric Corrosion by Compounds of the Triazole Class

Using a set of physicochemical (ellipsometry and contact angle measurements), electrochemical (electrochemical impedance spectroscopy and polarization measurements), and corrosion (periodic moisture condensation and salt fog tests) methods, the properties of adsorption films formed on copper by the chamber method from vapors of benzotriazol (BTA), 1H-1,2,4-triazole, tolyltriazole (TTA), 5-chloro-1,2,3-benzotriazole (CBTA), 3-amino-1H-1,2,4-triazole, and 4-amino-1H-1,2,4-triazole at a temperature of 100°C are studied. It is shown that 1-h chamber treatment of copper with vapors of these compounds leads to the formation of nanoscale hydrophobic adsorption films on it, which inhibits the thermal growth of oxides, but stabilizes the passive state of the metal and increases its corrosion resistance. Among these different triazole compounds tested as chamber corrosion inhibitors, BTA and its substituted derivatives are distinguished. After a 1-h chamber treatment of copper, the protective aftereffect of the adsorption films of triazole derivatives grows symbatically with their saturated vapor pressure at the chamber treatment temperature, i.e., in the following increasing order: CBTA < TTA < BTA. This may indicate that the equilibrium adsorption films do not have time to form at 100°С on the metal within this time period. After a prolonged (24 h or more) chamber treatment of copper with vapors of substituted benzotriazoles, equilibrium adsorption films of inhibitors are formed on it. In this case, the influence of the chamber inhibitor properties on their protective aftereffect alternates. Under such conditions, the least volatile and most hydrophobic substituted benzotriazole, i.e., CBTA, provide the best metal protection.

(Corrosion Division Morris Cohen Graduate Student Award Address) A Systematic Study of Critical Parameters Affecting the Galvanic Corrosion between Al Alloy and Stainless Steel in Atmospheric Condition

Connections between dissimilar materials are frequently encountered in complex structures involved in the aerospace industry. In a typical aircraft structure, one of the most common couples encountered is that of an aluminum-alloy-based airframe component and noble fasteners such as stainless steel. When this type of galvanic couple is exposed to a atmospheric marine environment, it can develop cracks that pose increased risk and require costly maintenance and repair. In this work, a complementary modeling and experimental approach is applied to systematically investigate the effect of electrolyte layer thickness, solution chemistry and materials surface properties on the electrochemical and corrosion distributions in the galvanic coupling between AA7050 and SS316L, and capture the underlying mechanism of the dependence of corrosion distributions on each external variable.To validate the robustness of our modeling approach, a Laplace-Equation based modeling coupled using mathematically-fitted electrochemical kinetics from experiment as boundary conditions was applied to simulate galvanic corrosion between Zn plate and SS 316 rods under thin layer electrolyte conditions. The modeling results were compared with experimental results from a four-day modified B117 test. It shows that: electrolyte layer thickness (WL)=3,500~4, 000 \U0001d707m would be the appropriate WL range formed on the sample surface during modified B117 salt fog testing; the robustness of Laplace-Equation based modeling is highly dependent on the boundary conditions, experimentally-determined electrochemical kinetics as boundary conditions can truly reflect the electrochemical response of anode/cathode to the surrounding solution environment, which in turn yields the simulated results mostly close to experimental measurement.In the study of the effect of electrolyte layer thickness, the total cathode current capacity of a surface on the electrolyte film thickness and cathode size in a galvanic couple to support the corrosion of AA7050 was accessed. The total cathode current capacity was studied over the range of WL thickness from full immersion conditions (where the total cathode current scales directly with cathode size) to the thin film regime in which the WL is the diffusion boundary layer thickness. In order to fully assess the transition from thin film to thick film condition, an understanding of the natural convection layer thickness is required. For the conditions studied here, the natural convection boundary layer was found to be close to 800 um. The WL thickness, cathode length and electrochemical kinetics interact to create four regimes of total cathode current as a function of WL thickness.In the study of the solution chemistry, the effect of Al3+ on the electrochemical and galvanic corrosion distributions between SS316L and AA7050was emphasized as it represents the major dissolved metal species from AA7050. It is found that Al3+ accelerates the hydrogen evolution reaction (HER) kinetics due to enhanced proton diffusivity, with the effect being observed not only on Al alloys, but also on Pt and stainless steel. The cation study for the galvanic couple indicates that Al3+ is also galvanic corrosion accelerator.The effect of oxide film properties on the cathodic kinetics of stainless steel were investigated because cathodic kinetics can significantly affect the degree of galvanic corrosion based on mixed potential theory. The study focused on the oxygen reduction reaction (ORR) and was studied by electrochemical (potentiodynamic polarization, cyclic voltammetry, potentiostatic test, and electrochemical impedance) techniques and x-ray photoelectron spectroscopy surface analysis. This study shows that the kinetics of ORR on stainless steels is determined by a combined effect of oxide film composition, film thickness, and resistivity.This work has improved the fundamental understanding of the effect of several pertinent variables on the galvanic-coupling induced localized corrosion of Al alloy, provided an approachable modeling means to predict corrosion distribution at given conditions in a timely fashion as well as develop corresponding corrosion mitigation strategies, and complemented continuum/meso-scale atmospheric corrosion modeling studies in this field. Acknowledgements The financial support from the Office of Naval Research (ONR) via Grants No. N00014-14-1-0012 and No. N00014-17-1-2033, the Sea-Based Aviation Program, and William Nickerson, Program Manager is gratefully acknowledged. The assistance of my advisor, Prof. R. G. Kelly is gratefully acknowledged. Helpful technical discussions with Profs. S. J. McDonnell, J. R. Scully, and J. T. Burns (University of Virginia), Dr. Jayendran Srinivasan (the Ohio State University), Dr. Piyush Khullar (Medtronic), Dr. Veronica Rafla (SpaceX) and Mr. Victor Yang (University of Virginia) are also acknowledged.

Corrosion Susceptibility and Allergy Potential of Austenitic Stainless Steels.

Although called stainless steels, austenitic steels are sensitive to localized corrosion, namely pitting, crevice, and intergranular form. Seventeen grades of steel were tested for localized corrosion. Steels were also tested in general corrosion and in galvanic couplings (steels–precious alloys) used in watchmaking applications. The evaluations have been carried out in accordance with the ASTM standards which specifically concern the forms of corrosion namely, general (B117-97, salt fog test), pitting (G48-11, FeCl3), crevice (F746-87) and intergranular (A262-15, Strauss chemical test and G108-94, Electrochemical potentiodynamic reactivation test). All tests revealed sensitivity to corrosion. We have noticed that the transverse face is clearly more sensitive than the longitudinal face, in the direction of rolling process. The same conclusion has been drawn from the tests of nickel release. It should be pointed out that, despite the fact that the grade of steel is in conformity with the classification standards, the behavior is very different from one manufacturer to another, due to parameters dependent on the production process, such as casting volume, alloying additions, and deoxidizing agents. The quantities of nickel released are related to the operations involved in the manufacturing process. Heat treatments reduce the quantities of nickel released. The surface state has little influence on the release. The hardening procedures increase the quantities of nickel released. The quantities of released nickel are influenced by the inclusionary state and the existence of the secondary phases in the steel structure. Another aspect is related to the strong dispersion of results concerning nickel release and corrosion behavior of raw materials.

Experimental investigation on corrosion behavior of friction stir welded AA7075-T651 aluminium alloy under 3.5% wt NaCl environment

The corrosion resistance of high strength heat treatable aluminium alloy is able to form an oxide film on its surface. In aggressive corrosion media, the oxide film can undergo corrosion responses in chloride-containing environments. The welding of AA7075 is important for advanced structural application in aircraft and automotive industries. Friction Stir Welding (FSW) method is the new technique and a sound welding method in the aluminium industry, which overcomes solidification cracking problem compared to the conventional fusion welding technique. Rolled plates of 10 mm thickness of AA7075-T651 were butt welded by using FSW process. The corrosion surface morphology and behaviour were investigated by conducting a salt fog test in sodium chloride solution at various spraying time, chloride ion and pH value. An objective was initiated to extend an experimental relationship to predict the corrosion rate of stir zone of FSW AA7075-T651 joints. Three factors five levels of a centre rotatable matrix was used to reduce the number of experimental circumstances and response surface methodology was used to develop an empirical relationship between salt fog variables. The empirical model can be used to predict the corrosion rate of FSW AA7075-T651 joints.

Polypyrrole/Metal Oxides-Based Composites/Nanocomposites for Corrosion Protection

Corrosion is of paramount interest of researchers all around the world owning to its disastrous impact on economy and safety. New strategies based on novel materials have been employed to mitigate corrosion. Conducting polymer-based nanocomposites is a class of materials which has shown promise for corrosion protection. This paper will focus on the specific case of the Conducting polymer-based nanocomposites for corrosion protection and one important case will be discussed in detail. Corrosion protection offered by Polypyrrole (PPy)/Fe2O3 based composite coating for cold rolled substrate is characterized in this paper by Electrochemical Impedance Spectroscopy (EIS) and Open Circuit Potential (OCP) measurements. It was found that PPy/Fe2O3 based composite coating provides better corrosion performance after 40 days exposure to ASTM B117 salt fog test conditions. This improved performance was attributed to the increased surface area of PPy and passivating nature of composite resulting from the redox activity provided by PPy.

Corrosion Behavior of Newly Developed High-Strength Bainitic Railway Wheel Steels

High-strength bainitic wheel steels based on a new steel composition, namely MS2 [0.47% C, 0.87% Mn, 0.51% Si, 0.02% Mo, 0.03%Cu, 0.031% S, 0.033% P and rest Fe (weight percent)], were prepared by austempering treatment at 400 °C for 10, 30, 60 and 120 min. Corrosion behavior of the bainitic MS2 steels and normalized ferritic–pearlitic MS2 steel was studied and compared with that of the conventional ferritic–pearlitic wheel steel. Immersion test, electrochemical polarization and salt fog tests were carried out in 3.5% NaCl. Bainitic steels prepared with higher holding duration during austempering exhibited improved corrosion resistance on salt fog exposure. In contrast, bainitic steels prepared with lower holding duration during austempering resulted in better corrosion resistance on electrochemical polarization test. Salt fog test revealed gradual improvement in corrosion resistance for the bainitic steels with the successive holding. Improved corrosion behavior for the bainitic steel was related to the tiny and uniform spreading of iron carbide in the ferritic matrix resulting in the uniform coverage of the protective oxide layer on the steel surface. The enrichment of Si on the corroded surface of bainitic steel favored the formation of supermagnetic α-FeOOH of smaller particle size, improving the protective character of the rust against corrosion. Corrosion mechanisms for the ferritic–pearlitic and bainitic wheel steels were put forward.

Corrosion protection of carbon steel by polyurethane coatings containing graphene oxide

AbstractIn this work, graphene oxide (GO) was prepared by modified Hummer's method. Polyurethane coatings with different GO concentrations (0.1‐0.5 %) were prepared for corrosion protection of carbon steel. Synthesized GO was characterized by FTIR and XRD. Corrosion resistance of polyurethane coatings containing GO was investigated by electrochemical impedance spectroscopy and salt fog test. The effects of GO on protection performance of polyurethane coatings depended on its dispersion ability. GO at a concentration of 0.1 % significantly improved corrosion resistance of polyurethane coatings.

Corrosion resistance of optical diamond-like carbon film

KrF laser and Ti:Sapphire femto-second laser were used to deposit diamond-like carbon(DLC) films on silicon substrates which were double polished. Optical transmittance and corrosion resistance of these samples were compared. The transmittance of DLC film sample which was deposited by Ti:Sapphire laser in oxygen atmosphere was higher than the sample which was deposited by KrF laser in vacuum. Both samples could pass the salt solubility test and salt fog test. But when dipped in NaOH liquor, the result showed that surface of the sample deposited by Ti:Sapphire laser in oxygen atmosphere appeared corrosive spots first. Reasons were analyzed according to corrosive mechanism.

Pengaruh Rapat Arus Proses Continuous Hard Anodizing Elektrolit (H2SO4) terhadap Laju Korosi Pipa Aluminium 6061 dengan Pengujian Kabut Garam

Anodizing is an electro-chemical process used to coat metal surfaces with a stable oxide layer. The function of this oxide layer is to increase corrosion resistance. The purpose of this study is determine the effect of variations in current density on the continuous hard anodizing process carried out in sulfuric acid electrolyte solution (H2SO4) on the corrosion rate of aluminum alloy 6061. Corrosion rate testing is carried out through salt fog testing. The values of the current variation used are 1 A/dm2; 2 A/dm2; 3 A/dm2; 4 A/dm2; and 5 A/dm2. Statistical calculations using the analysis of variance proved the current density in the anodizing process has a significant effect on the corrosion resistance of the anodizing workpiece. Corrosion testing provides information that the highest corrosion rate is an anodizing workpiece with a current density of 1 A/dm2, which is 125.6861 mdd, then 2 A/dm2 of 104.33333 mdd. The lowest corrosion rate value obtained at the use of current density 3 A/dm2, that is 51,8083 mdd. Meanwhile, the use of current density of 4 A/dm2 has a slightly higher corrosion rate compared to the use of current density of 3 A/dm2, which is 86.5444 mdd. Furthermore, the use of current density of 5 A/dm2 has the highest decay rate, so that the formed oxide layer will be damaged, as seen from the higher corrosion rate of the material, which is 100.8361 mdd.

AGEING STUDY OF HIGH VOLTAGE INSULATOR WITH NANO FILLERS

Silicon insulating materials with Nanofillers have attracted wide interest for enhancing electrical properties. In this work the experimental results of silicone rubber[SiR]nano based polymer outdoor insulators in salt fog ageing test based on IEC 62217 are presented. The specimen made of composite material by adding MgO and ZnO as Nano filler to Silicone Rubber as the base polymer with ATH. The samples prepared consists of Virgin without any nano filler as the reference , 10% MgO, 10% ZnO, 5% MgO, 5% ZnO nano-composite insulators. These five samples are kept in artificial salt fog chamber and aging test was conducted for a duration of 1000 hrs. Reduction of hydrophobicity, level of contamination are used as physical damaged inspection techniques were used to evaluate degree of surface deterioration. Differences in degree of surface deterioration were observed on all tested specimens just after salt fog test. It is observed that all the insulator withstood the test sample except with 10%MgO which have failed after 720 hrs of exposed to salt fog. All the samples performed well in inclined plane, tracking and erosion test. XRD on all samples before and after the test were carried out.

Comparative Study of HVOF-Sprayed NiCrBSi Alloy and 316L Stainless Steel Coatings on a Brass Substrate

Brass alloys are used in many applications. However, improving their surface properties would help to increase their service life. For that, this study proposed to deposit using high velocity oxygen fuel (HVOF), nickel-chromium-boron-silicon (NiCrBSi) alloy, and 316L stainless steel (SS) coatings on brass substrates and investigate the mechanical properties and corrosion resistance of the coatings. The surface–interface morphologies, phases, and porosity of the coatings were analyzed using a scanning electron microscope and 3D profilometer. The adhesive strength and microhardness of the NiCrBSi and 316L SS coatings were also studied. Corrosion investigations were carried out using the salt fog test in an acetic acid salt spray atmosphere according to the NF EN ISO 9227 standard. This work showed that the 316L SS coatings presented a lower microhardness and higher adhesion strength than the NiCrBSi coatings despite their lower corrosion resistance. This could be explained by the microstructure of the coatings, the 316L SS coatings exhibiting more defects such as pores, un-melted particles, and oxides.

Comparative Evaluation of Corrosion Effects between Nanocrystalline Silver Alloy and Tradition Gold Stacks Using Spring Probe Contacts

Although silver is evaluated as an alternative of gold, it is more prone to tarnishing, oxidization and corrosion. Recent advancements in nano materials research resulted in a nanocrystalline silver alloy which has several advantages like high hardness, thermal stability, non-coarsen with age, hence a viable solution for connector applications. In this work, the performance of nanocrystalline silver alloy against corrosion was studied. Two different set of spring probes were electroplated on inner and outer regions and tested using force deflection resistance (FDR), life cycle test (LCT), SEM, EDS and X-Ray CT scan. First set of spring probes were electroplated with nanocrystalline silver alloy, nanocrystalline Ni-W, Ni sulfamate and Ni strike with thicknesses of 2.4 µm, 1.8 µm, 2.0 µm and 0.5 µm respectively. Second set of spring probes were electroplated with Gold, Ni sulfamate and Ni strike with thicknesses of 0.9 µm 1.9 µm and 0.5 µm respectively. The body of spring probes was made up of copper alloy. This work reports the changes in electrical, mechanical and material properties of nanocrystalline silver alloy and gold stacks after reliability operations like humidity test for 24 hours and 96 hours, porosity test for 60 mins and salt-fog test for 24 hours. Although hard gold is preferred as a final finish for contacts, the demand of finding its alternative has increased because of increase in market price. Further, practices to reduce gold thickness increase the porosity of gold layer which inversely effects the performance of connectors. Nanocrystalline silver alloy is a potential candidate as an alternative of gold in high speed applications [1]. It behaves differently than pure silver because its thermally stable nanostructure improves hardness and eliminates surface sulfidation [2]. All tests in this work were performed on spring probes which is one of the products of Smiths Interconnect used for contacts and connector applications [3]. In FDR, the spring compressed from normal position to 0.14 inch and extended back to normal position. By this way, it completes a hysteresis and measures coefficient of friction between barrel and plunger of spring probes. After reliability operations, the highest compression force in the case of gold was reached up to 12 oz and in the case of nanocrystalline silver alloy, it reached up to 9.5 oz. The difference in the magnitude of compression and extension force at 0.14 inch measures friction. Higher difference between these two forces measures lower Q values which result in higher coefficient of friction. After reliability operations, the range of this difference was from 6 oz to 7 oz in the case of gold but in the case of nanocrystalline silver alloy this range was from 3.5 oz to 4 oz. Moreover the difference in resistance during compression and extension was 2 mΩ in the case of gold and 1 mΩ in the case of nanocrystalline silver alloy. Meaning the alloy of nanocrystalline silver did not allow silver sulfidation. In life cycle test (LCT), 32 spring probes were installed into receptacles that have been press fitted into a matrix of holes drilled into fiber block and the resistance was measured in 10,000 life cycles. The maximum resistance was reached up to 11 mΩ in the case of gold stack but in the case of nanocrystalline silver alloy it was reached up to 8 mΩ only. In the reliability tests, many probes failed to measure contact resistance in the case of gold stack, but in the case of nanocrystalline silver stack it maintained below 6 mΩ. This means that the failure of probes was limited by the wear performance of the gold in the mating pair between barrel and plunger. The failed probes in reliability operations were tested using front and cross section SEM and the elemental composition was observed using point and line scan of EDS. The mechanical marks, which is a function of wear rate, were observed in SEM on the inner regions of the probes at the mating of barrels and plungers. The failure of the probes was further tested from X-Ray CT scanning. In the final version of the manuscript additional results and discussions will be presented.

Exploring the Effects of Nanofillers of Epoxy Nanocomposite Coating for Sustainable Corrosion Protection

Development of coating durability and sustainability for industry to facilitate the corrosion potential minimization attract much attention in recent year. The selection of appropriate coating material is necessities to improve corrosion protection of metal. Epoxy nanocomposite coatings filled with different amount of graphene nanoplateles (GNP) and montmorillonite (MMT) was prepared via mechanical agitation process to enhance the flame retardancy and anticorrosion performance of mild steel substrates. Salt fog test, limiting oxygen index (LOI) and water absorption result reveal that embedding a small amount of filler remarkably improved anticorrosion performance and flame retardancy of epoxy nanocomposite coatings. Present study suggests a development of nanocomposite coating with superior mechanical properties which was evaluated by adhesion tape test.

Influence of Moist Environment on Aging Performance of Energized Silicone Rubber Used for Outdoor Insulation

The influence of moist environments on the aging performance of silicone rubber (SR) used for outdoor insulation was investigated by a salt-fog test. High-temperature vulcanized (HTV) SRs with different alumina trihydrate (ATH) filler contents were adopted as the test specimens. For the test of a single water droplet, the vibration and elongation of the water droplet caused a flashover, and the flashover voltage decreased with increasing ATH content. In the first cycle of the salt-fog test, the leakage current increased with increasing ATH content. The relatively higher hydrophobicity of the specimen with a low ATH content than the specimen with a high ATH content had an inhibitory effect on the initial leakage current development. In the last cycle of the salt-fog test, the heat from dry band arc discharge became the dominant factor affecting the surface aging after the loss of hydrophobicity, and the specimen with a higher ATH content inversely had a better inhibitory effect on leakage current development. According to the X-ray photoelectron spectroscopy (XPS) analysis results, when the energized SR was exposed to a moist environment, the heat from dry band arc discharge and the hydrolysis reaction caused a change in the binding state between Si and O, which is considered the mechanism responsible for material degradation. During this process, the higher content of ATH had a remarkable effect on alleviating surface aging.

Influence of Salt Fog Test on Silicone Rubber Insulating Material Under AC and DC Voltages

The present work investigates the performance of electrically stressed silicone rubber insulating material in a cyclic salt fog test. Corona Inception Voltage due to water droplet initiated discharges changes after salt fog ageing. The Ultra High Frequency signals radiated during corona discharge activity under AC voltages have a frequency span of 0.8–1.5 GHz, whereas under DC voltages span lies in the range of 0.5–1.5 GHz. Contact angle reduces with the increase in number of salt fog ageing cycles. Surface potential accumulation studies indicate that salt fog aged silicone rubber shows characteristic variation in accumulated potential magnitude and the decay characteristics. Further tdv/dt of surface potential decay characteristics enables to understand the charge penetration depth. Weight loss studies and surface roughness analysis during salt fog test are used to quantify the amount of damage.

Equivalent Salt Deposit Density Prediction of Silicone Rubber Insulators Under Simulated Pollution Conditions

Insulator flashover happens when soluble and/or non-soluble contaminants cover the insulator surface which results in a reduction of the surface resistance. Significant research has been conducted to utilize leakage current (LC) to predict the contamination level on the outdoor ceramic insulators surface. This can help as a mean to warn overhead lines operators about the advent of insulator flashover. However, there have been few attempts to predict the contamination levels on the surface of non-ceramic insulators. This work aims to develop a non-intrusive technique to monitor and evaluate the surface condition of silicone rubber (SIR) insulators by predicting the equivalent salt deposit density (ESDD). Three different classifiers (K-Nearest Neighbor Classifier (KNN), Polynomial, and Neuro-fuzzy) have been utilized to predict the ESDD level of SIR samples after a salt fog test. Moreover, stepwise regression and principle component analysis (PCA) have been used as feature selection tools to optimize the classification process. The overall prediction accuracy improved from 68% to 95% when the number of classes reduced from four to two respectively.

NiCrNx interlayer thickness dependence of spectral performance and environmental durability of protected-silver mirrors

Gemini-style protected-silver mirror (Sub/NiCrNx/Ag/NiCrNx/SiNx/Air) is a suitable choice for optical instruments requiring both long-term environmental durability and high broadband reflectance. Three Gemini-style protected-silver mirrors with NiCrNx interlayer thicknesses between 0.1 and 0.6 nm were prepared by magnetron sputtering, and the dependences of spectral properties and environmental durability of these protected-silver mirrors on the thickness of NiCrNx interlayer between the silver layer and SiNx layer were investigated in-depth. The reflectance, transmittance and total scattering loss measurements, optical microscope, and scanning electron microscope imaging were employed to characterize the spectral properties and surface morphology, and accelerated environmental tests, including humidity test and salt fog test, were applied to investigate the environmental durability. The experimental results showed that both optical and corrosion-resistant properties of protected-silver mirrors were NiCrNx interlayer thickness dependent, and an optimum NiCrNx interlayer thickness should be similar to 0.3 nm for Gemini-style protected-silver mirrors to have reasonably both high reflectance in a broadband spectral range from visible to far infrared and good corrosion resistance for long-lifetime applications in harsh environments. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)