Volume 22 Preprint 55


Enhancement of the Corrosion Resistance of Fastening System of Ballasted ??Railway in Sandy Desert by Using Nano-coating

Milad Alizadeh Galdiani‎, Navid Sabet‎‎, Mohamad Ali Mohit

Keywords: nano-coating, corrosion, railway fastening system, sandy desert, ballasted railway

Abstract:
Railway as one of the most important transportation modes, passes through ‎various areas with different conditions ‎inevitably, and in many countries such as ‎China, United States, Australia and Iran, it passes through sandy ‎desert areas. One ‎of the main problems in these areas is the movement of sand causing various ‎damages ‎to ballasted railway track such as corrosion in railway fastening system. ‎The soil composition of some desert areas like Fahraj in Iran consists of sand ‎and ‎salt. Due to the movement of sand and corrosive ions of salt, the fastening system ‎of railway is ‎corroded, which in turn, reduces the thickness of the components ‎and their life span.‎ In this research, the nano-coating for fastening system of ‎railway is ‎introduced, and its performance has been investigated in both ‎laboratory and field tests. The Nano-coating of ‎fastening system consists of zinc ‎rich, epoxy, polyurethane and additive which is produced through ‎Nano ‎technology. This layer covers the surface of the fastening system and ‎prohibits the chemical reactions which result in ‎corrosion. The results of ‎Electrochemical Impedance Spectroscopy (EIS) ‎indicate that corrosion resistance ‎increases 315 times by using nano-coating, salt spray test results demonstrate that ‎nano-coated components remained intact after 1000 hours.‎

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Enhancement of the Corrosion Resistance of Fastening System of Ballasted Railway in Sandy Desert by Using Nano-coating Milad Alizadeh Galdiani1*, Navid Sabet2, Mohamad Ali Mohit3 1 Administration of Railway Track and Technical Structures, Islamic Republic of Iran Railways Company (RAI), Room 215, Noori Building, Rahahan Square, Tehran Province, Islamic Republic of Iran, alizadeh_mi@rai.ir 2 Administration of Kerman Province Railway, Islamic Republic of Iran Railways Company (RAI), Room 31, CTC Building, Rahahan Square, Kerman Province, Islamic Republic of Iran, sabet_s@kerman.rai.ir 3 Administration of Railway Track and Technical Structures, Islamic Republic of Iran Railways Company (RAI), Room 215, Noori Building, Rahahan Square, Tehran Province, Islamic Republic of Iran, mohit_m@rai.ir Abstract Railway as one of the most important transportation modes, passes through various areas with different conditions inevitably, and in many countries such as China, United States, Australia and Iran, it passes through sandy desert areas. One of the main problems in these areas is the movement of sand causing various damages to ballasted railway track such as corrosion in railway fastening system. The soil composition of some desert areas like Fahraj in Iran consists of sand and salt. Due to the movement of sand and corrosive ions of salt, the fastening system of railway is corroded, which in turn, reduces the thickness of the components and their life span. In this research, the nano-coating for fastening system of railway is introduced, and its performance has been investigated in both laboratory and field tests. The Nano-coating of fastening system consists of zinc rich, epoxy, polyurethane and additive which is produced through Nano technology. This layer covers the surface of the fastening system and prohibits the chemical reactions which result in corrosion. The results of Electrochemical Impedance Spectroscopy (EIS) indicate that corrosion resistance increases 315 times by using nano-coating, salt spray test results demonstrate that nanocoated components remained intact after 1000 hours. Keywords: nano-coating, corrosion, railway fastening system, sandy desert, ballasted railway 1 Introduction Among all types of transportation systems, railway transportation is one of the best, since in comparison with other transportation systems, railway vehicles consume less fuel for transit, have fewer repercussions for the environment, and provide much higher level of safety for passengers. Cost of maintenance in railway industry is considered as an imperative matter and that is why the railway experts put a lot of time and effort into lowering this cost[1]. Due to the nature of transit via railway, railway tracks inevitably pass through various types of areas including deserts and wasteland. As a consequence, the maintenance of railway tracks is always a serious concerning problem. In deserts for instance, the movement of sand dunes might lead to inevitable problems in the railway track. Despite the higher maintenance cost associated with passing the railway tracks through deserts compared to areas with normal conditions, in many countries including Australia, the United States, China and Iran, railway tracks pass through these sandy regions. For example, more than 400 km of the Iranian railways pass through sandy desert areas. The movement of sand dunes causes some problems such as increasing the rigidity of ballast layer, corrosion in rail and railway fastening system, and the reduction in strength of concrete sleepers in ballasted tracks. Although a wide variety of solutions have been proposed, none of them have been completely feasible in addressing the mentioned problems. One of the rudimentary approaches to deal with the movement of sand dunes in desert areas is planting, which is an effective method to control erosion. Reducing wind speed near the surface of the ground is the mechanism of this approach which has turned to be effective in terms of preventing the sand dune movement. To fulfil the aims of this method, the type of the employed flora is selected based on the environmental conditions classifying into shrubs and trees. There is a direct correlation between the number of shrubs and trees in sandy areas and the amount of accumulated sand. Therefore, sand movements are controlled more effectively as the plants grow in desert areas. Another important point about planting in desert areas is the pattern of plants; for instance, the checkered pattern and also plants with particular shape such as straws and rice that are commonly twisted together, control the sand movement very efficiently. This method could not be applied in every desert area due to some limitations including the water shortage and the small number of plants growing and surviving in these areas[1], [2]. Another approach that has been conducted in order to prevent sand movement is embankment and trenches which are the most preliminary methods for the stabilization of sand dunes. This method is usually accompanied by other techniques of sand dune stabilization and is considered as one of the most effective approaches to solve the 2 problem provided that it is applied according to the standards. This method goes a long way towards reducing the wind speed, and as the previous observations have proven, its highest performance is achieved when the wind and the trenches directions are perpendicular. In spite of its promising performance, this method suffers from a number of limitations. Namely, the dug trenches are gradually filled by sand dunes over time, which in turn, results in extra sand dunes passing over the trenches, leading to the system malfunction. Therefore, this method is not suitable for critical sandy regions[1]. Another method to control sand dune movements is implementing deposition traps with basically the same functionality as the trench method but with a different size. These traps are smaller than trenches and that is why vegetation is often used to enhance their performance. The number of deposition traps is directly related to the volume of sand in the sandy area. This method has the same disadvantages as the trench method, and therefore, it is not recommended for critical areas in which the volume of sand is high[1], [3]. Construction of walls in order to protect railways against sand storm in desert areas is one of the most common methods in railways that have been applied in many cases. To construct this kind of walls, various materials such as wooden and metal sleepers are utilized. In some cases, precast concrete walls and retaining walls are used, as well. In the Iranian railways, walls, made of second-hand wooden sleepers, have been constructed, and the observations of them indicate that there is a meaningful relationship between direction of sand deposition and direction of railroad track. The best performance of these walls occurs when the direction of walls is perpendicular to the wind direction[4]–[6]. In this approach, applying a slope with gradient of 10 degrees in the upper 30 cm of the precast concrete wall makes sand dunes to pass over the wall and over the railway track and to accumulate in far areas during the sand storms. The advantage of the precast walls is that they are portable, and can be re-used in other areas with the same problem. However, regular concrete, used in buildings, cannot be applied in all desert areas due to presence of a lot of harmful chemicals that are corrosive and have negative effect on concrete walls. As a result, in many cases, the concrete for construction of the walls should be prepared in a special way and it is considered as a disadvantage of this method[5], [6]. Chemical stabilization of sand dunes has been introduced in Iran in recent decades. Different kinds of mulches have been made and several studies have been carried out in order to evaluate the performance of the sand dunes stabilization. Mulches are used for two purposes in railway industry: First, in order to stabilize the sand around the railway tracks and to obstruct their movement, and second, to create a cover for the embankments to prevent damage to the 3 substructure of railway tracks[7], [8]. There are various types of mulch such as oil mulch, calcium chloride mulch, magnesium chloride mulch, polylatis polymer mulch and calcareous clay mulch. Oil mulch is sprayed on the surface of the sand as an emulsion and over the time, the water in the emulsion is evaporated, consequently a heavy oil layer remains that stabilizes the sand. In some cases, the side effects of oil mulch on the seedling of the local plants have been observed, which is considered as a disadvantage of this method because the plants themselves are one of the main reasons for the stabilization of the sand[7], [8]. Calcium chloride mulch, as a stabilizer for roads, has an acceptable performance but its main disadvantage is its solubility in water. During extreme rainfalls, this material is dissolved in water and leads to loss of the stabilizing characteristics of mulch. Another feature of this mulch is crystallization in the cold weather as it precipitates in winter season and forms crystals[7], [8]. Polylatis polymer mulch has no side effect on permeability of soil; consequently water is conducted properly for establishment of green plants. However, in comparison with the oil mulch, this method has a serious negative effect on plant growth, especially plant seedling; which is due to better performance of oil mulch in stabilizing sand dunes. Calcareous clay mulch is composed of clay, lime and water, and it has an acceptable performance against the wind. Due to the abundance of materials in the local environment, it is economical to use this approach and because of lime and effects of that on plants, more studies are needed[7], [8]. One of the major problems of ballasted railway tracks in the sandy regions is contamination of ballast layer which results in increasing the rigidity of the track system, and causing problems such as increasing dynamic forces, reducing speed of rolling stock, and increasing the maintenance costs. A solution to this problem is application of slab track system. Although in this system, the maintenance costs are reduced, it needs a huge investment for construction and provides insufficient performance in areas where the volume of sand is considerable[9]. The humpback slab track is a special type of slab track, which is designed for desert areas. In this method, creating geometric changes in the rail seating area of slab track makes the sand dunes pass through the rails and fastening systems, and therefore, the accumulation of sand along them is prevented. Although in comparison with conventional slab track, this method has better performance in desert areas, but it is not applicable to areas with high volumes of sand[1], [9]. Lightweight concrete gallery and metal gallery are other approaches that are the most appropriate types of galleries for desert areas, and are suitable for light loads such as sand dunes. Preventing sand dunes from accumulating in railway track system and low maintenance costs are some of the main advantages of this approach. On the other hand, limiting repair operations, high initial investment for construction are the downsides associated with implementation of this method[1]. In this 4 research nano-coating of fastening system will be presented as a new method to enhance corrosion resistance against corrosive salty sand in desert areas. Materials and Methods Anti-Corrosion Nano-Coating In this research, the Nano-coating for fastening system of ballasted track is introduced as a solution to prevent the corrosion in rail clips and screw spikes which is due to effects of sand dunes, and performance of that is evaluated in a laboratory and field test on the railway track. Corrosion as an electrochemical reaction causes the metal to be converted to metal ion. In sandy regions, the accumulation of sand on the track causes the rail foot and the sleeper and fastening system to corrode. Nano-coating of fastening system in ballasted track (rail clips and screw spikes) is composed of upgraded zinc-rich and epoxy, an additive which is produced by Nano-technology and polyurethane and its chemical formula is (TiO2 PPY/Sn-doped) + (Zinc-Rich). Based on the amount and composition of the ingredients and the final cost of the product, Nano-coating is classified to three categories[10]–[12]. This classification of coatings based on the amount of ingredients (grams) for covering a fastening system of railway track is proposed in table 1. The three above mentioned Nanocoatings are affordable economically and the cost of implementing them is less than 5% of the cost to manufacture a set of ballasted track fastening system and the first and third class has highest and lowest prices, respectively. In this research, all of the three products are used in the field tests but for the laboratory test the third class is used, which has the lowest price in comparison with other products. Table 1. Classification of coatings for fastening system. Class no. Upgraded zinc-rich+additive(g) Upgraded epoxy primer+additive(g) Second epoxy layer(g) Polyurethane(g) 1 60 - 40 40 2 - 40 30 40 3 - 50 - 30 Corrosion Measurement Experiments There are a large number of various laboratory methods such as Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS) in two modes of potentiostatic and galvanostatic, and salt spray to measure the corrosion resistance of 5 coatings. Due to salty nature of sand dunes in desert areas which increases corrosive function, EIS and salt spray in the laboratory phase are used to evaluate the performance of the Nano-coating. EIS is an electrochemical method in which an electric potential difference is applied and its relevant electrical current is measured and the corrosion rate and other electrochemical factors can be measured by using the relationship between applied electric potential and relevant electrical current. The basis of this method is the measurement of the alternating current (AC) impedance at a range of frequencies. In this method, a small electric potential close to the open circuit potential is applied variably by the time to the sample, which does not damage the sample. The results can be plotted on the basis of Nyquist plots (real impedance and imaginary impedance) or Bode plots (absolute value of impedance or angle of phase in terms of frequency), which in this research Nyquist plots have been used to express the corrosion rate. Because there is no potential sweeping in the impedance method, measurements can be done in low conductivity solutions. While in direct current (DC) methods, such solutions are highly exposed to potential control errors. The most important advantage of the impedance method compared to other alternating current methods is that it provides an equivalent electrical model for the electrochemical phenomenon[10], [12]–[16]. Salt spray is a standard test utilizing to evaluate corrosion resistance. This method is a fast corrosion test that provides a controlled corrosive environment which has been utilized to produce relative corrosion resistance information for metals or coated metals exposed in a given test chamber. Performance of metal or coated metal against natural corrosive environments has meaningful relationship with salt spray results; consequently the corrosion performance of metal can be predicted. ASTM B 117 is applied as common standard for salt spray test. In this method after primary preparation, the samples should be situated in proper position at angel of 15 to 30 degrees to vertical axis of salt flow and surface of samples should be faced up. During the test, samples should not interact with each other or with any other metal materials. Usually, the saline solution that used in this test consists of 5 percent salt (NaCl) and 95 percent distilled water, and the maximum allowable salt intake is less than 0.3%. The standard environmental conditions of salt spray test (salt fog or salt spray) are included the pH of the salt solution 6.5-7.2, the spraying pressure of the salt solution is 1.24-0.83 bar, and the temperature of the spray booth is 35 ± 2 ° C[13], [17], [18]. Results and Discussion In the EIS test, Pandrol and Vossloh fastening systems including screw spikes and rail clips were investigated. The test has been done in two groups of fastening system with Nano6 coating and fastening system with conventional coating without Nano-coating in order to compare the test results and measure the effect of Nano-coating on decreasing the rate of corrosion. Experiments were carried out in the frequency range of 5Hz to 70 kHz and disturbance amplitude of 10 mV. Sand samples are collected from the local environment which were saturated and kept at 45°C and sprayed with solution of 1.5% sodium chloride every day. After 60 days, corrosion rate of samples were examined by EIS test. Nyquist curves of EIS test for samples with conventional coating and with Nano-coating are shown in figure 1. Figure 1. Nyquist curve of sample without Nano-coating (left) Nyquist curve of sample with Nano-coating (right). According to the figures 1, the Nyquist curves of the samples indicate that real impedance (Z’) is increased for 315 times in diagram of Nano-coating in comparison with diagram of conventional coating without Nano additive which it proves that corrosion resistance of fastening system with Nano-coating is stronger than fastening system with conventional coating and corrosion resistance increases 315 times in fastening system with Nanocoating. In this research, a salt spray test was conducted for two times on fastening system with Nano-coating and fastening system without Nano coating and the results of this test are attached in appendices. Based on the results, the surface of the sample without Nanocoating began to corrode after 24 hours of spraying, and after 168 hours, 100% of the surface of the sample was corroded. The results of the test on fastening system with Nanocoating indicate a noticeable increase in corrosion resistance, after 1000 hours of spraying 7 on sample of the test, no corrosion has been observed at the screw surface, which indicates that the Nano-coating has a significant role in corrosion resistance. The images of the rail clips and screw spikes with and without Nano-coating used in the salt spray test are shown in figures 2 to 5. Figure 2. Screw spike without Nano-coating before salt spray test (left) Screw spike without Nano-coating after salt spray test(right). Figure 3. Screw spike with Nano-coating before salt spray test (left) Screw spike with Nanocoating after salt spray test (right). 8 Figure 4. Rail clip without Nano-coating before salt spray test (left) Rail clip without Nanocoating after salt spray test (right). Figure 5. Rail clip with Nano-coating before salt spray test (left) Rail clip with Nano-coating after salt spray test (right). Field Investigation In order to conduct field experiments, primarily the railway tracks passing through the sandy desert areas were considered. The site should be located in areas which corrosion rate is high and finally the sandy region between Fahraj railway station and Shoorgaz railway station in Kerman state railway administration in Iranian railways was investigated, which due to the movement of sand dunes is one of the areas that corrosion rate is noticeably high. To evaluate Nano-coating performance against corrosion, some fastening systems with conventional coating should be replaced with fastening system with Nanocoating which are shown in figure 6. The installation team was educated how to prepare the Nano-coating and when to replace conventional coating with Nano-coating. After the first survey to the site of operation, corrosion in screw spikes, rail clips and rail foot was obvious as shown in figure 7. 9 Figure 6. Fastening system with Nano-coating installed in the site. Figure 7. Effect of sandy desert on corrosion of metallic components. In the process of applying Nano-coating, many conditions of the local environment should be considered such as traffic, temperature and wind speed. Thus at the beginning of the day before increasing the site temperature, the first layer of Nano-coating was performed as undercoat, and at the end of the day, again with the reduction of the temperature, the second layer was coated. The important point about the second layer is that it does not include any Nano-additive which results in decreasing the final cost of the Nano-coating. In order to compare performance of Nano-coating with conventional coating some new fastening systems with conventional coating replaced in the site. Three and 12 months after exerting Nano-coating, to verify the performance of Nanocoating against corrosion, two surveys were carried out, which proved that fastening systems with Nano-coating have higher corrosion resistance against sand dunes. After the first survey, three months after the implementation of the pilot sample, the performance of the Nano-coating was completely acceptable. The performance of fastening system with Nano-coating and fastening system without Nano-coating could be compared in figure 8. 10 Figure 8. Fastening system with Nano-coating 3 months after installation (left) Fastening system without Nano-coating 3 months after installation (right). Due to the environmental conditions, to exert the Nano-coating, it is better to coat the screw spikes and clips with Nano-coating in laboratory and then install them in the site; and finally, if some screw spikes lost their coating because of the installation process in the site of operation, they should be coated again. Applying Nano-coating in this way can increase the useful lifespan. Images of the survey one year after performing the Nanocoatings indicate the acceptable performance of the Nano-coating against corrosion, while other fastening systems without Nano-coating should be replaced due to excessive corrosion. These results are shown in figure 9. Figure 9. Fastening system with Nano-coating 12 months after installation (left) Fastening system without Nano-coating 12 months after installation (right). Conclusion Passing railways through sandy desert areas all over the world is inevitable, and in Iran, Kerman state railways pass through these sandy desert areas. The movement of sand dunes which causes problems such as chemical attacks on the railway track, contamination of ballast layer and increasing track rigidity, is the main problem in these areas and always causes damage to the railway tracks. The corrosion of fastening system causes damages to superstructure components which is due to salty sand dune attacks, and results in significant increase in maintenance costs. Various strategies have been proposed to prevent the destructive effects of the movement of sand dunes; none of them have completely solved this problem. Nano-coating of fastening system for ballasted railway track in sandy desert areas is an invention including epoxy and upgraded zinc rich, an additive which made based on Nano-technology and polyurethane. This material as a coating prevents the chemical reaction leading to corrosion. The results of laboratory experiments (EIS test and 11 salt spray test) on fastening system with Nano-coating and fastening system without Nanocoating indicate that corrosion resistance of fastening system with Nano-coating increases more than 315 times compared to conventional fastening system without Nano-coating and Nano-coated screws and clips were completely sound after 1000 hours of salt spray. The results of field investigation of fastening systems with Nano-coating in Kerman state railway administration of Iran (Shoorgaz-Fahraj block) prove a significant increase in corrosion resistance of fastening system with Nano-coating. After one year of applying fastening system with Nano-coating in the site, conventional fastening system should be replaced, while fastening system with Nano-coating operate properly without any corrosion. From an economic point of view, to increase the corrosion resistance of fastening system by using this approach, it is quite cost effective due to the low cost of Nano-coating materials and this method reduces maintenance costs as well. References [1] L. Bruno, M. Horvat, and L. Raffaele, “Windblown sand along railway infrastructures: A review of challenges and mitigation measures”, Journal of Wind Engineering & Industrial Aerodynamics, 177, pp. 340–365, 2018. [2] Y. Chen, Z. Zhang, L. Huang, Y. Zhao, Y. Hu, and P. Zhang, “Co-variation of fine-root distribution with vegetation and soil properties along a revegetation chronosequence in a desert area in northwestern China”, Catena, 151, pp. 16–25, 2017. [3] J. A. Zakeri, “Investigation on railway track maintenance in sandy dry areas”, Structure and Infrastructure Engineering: Maintenance, Management, Life-Cycle Design and Performance, 8:2, pp. 37–41, 2012. [4] K. Zhang, J. Qu, K. Liao, Q. Niu, and Q. Han, “Damage by wind-blown sand and its control along Qinghai-Tibet Railway in China,” Aeolian Research, 1, pp. 143–146, 2010. [5] J. Cheng and C. Xue, “The sand-damage-prevention engineering system for the railway in the desert region of the Qinghai-Tibet plateau”, Journal of Wind Engineering & Industrial Aerodynamics, 125, pp. 30–37, 2014. [6] L. Bruno, D. Fransos, and A. Lo, “Solid barriers for windblown sand mitigation: Aerodynamic behavior and conceptual design guidelines,” Journal of Wind Engineering & Industrial Aerodynamics, 173, pp. 79–90, 2018. 12 [7] S. M. Abtahi, “The effect of cellulose polymer mulch on sand stabilization” Polimery, 10, pp. 575, 2017. [8] B. K. Moghadam, T. Jamili, H. Nadian, and E. Shahbazi, “The influence of sugarcane mulch on sand dune stabilization in Khuzestan, the southwest of Iran Article history:” Iran Agricultural Research, 34, pp. 71–80, 2015. [9] H. P. Samadi, J. A. Zakeri, and G. N. Bidhendi, “Effect of Constructing Canal in Embankments on Sand Flow through Railway Tracks in Desert Regions,” International Journal of Transportation Engineering, 6, pp. 395–407, 2018. [10] A. Gergely, I. Bertóti, T. Török, É. Pfeifer, and E. Kálmán, “Corrosion protection with zinc-rich epoxy paint coatings embedded with various amounts of highly dispersed polypyrrole-deposited alumina monohydrate particles”, Progress in Organic Coatings, 76, pp. 17–32, 2013. [11] A. Gergely, É. Pfeifer, I. Bertóti, T. Török, and E. Kálmán, “Corrosion protection of coldrolled steel by zinc-rich epoxy paint coatings loaded with nano-size alumina supported polypyrrole”, 53, pp. 3486–3499, 2011. [12] A. Anandhi, S. Palraj, G. Subramanian, and M. Selvaraj, “Corrosion resistance and improved adhesion properties of propargyl alcohol impregnated mesoporous titanium dioxide built-in epoxy zinc rich primer”, Progress in Organic Coatings, 97, pp. 10–18, 2016. [13] M. Huang and J. Yang, “Salt spray and EIS studies on HDI microcapsule-based selfhealing anticorrosive coatings”, Progress in Organic Coatings, 77, pp. 168–175, 2014. [14] T. Saravanakumar, V. Kavimani, K. S. Prakash, and T. Selvaraju, “Exploring the corrosion inhibition of magnesium by coatings Formulated with nano CeO 2 and ZnO particles”, Progress in Organic Coatings, 129, pp. 32–42, 2019. [15] M. Mobin, J. Aslam, and R. Alam, “Anti-corrosive properties of Poly(aniline-co-2,3xylidine)/ZnO nanocomposite coating on low-carbon steel”, Journal of Adhesion Science and Technology, 4243, 2016. [16] J. Yu, S. Akira, and I. Masahiro, “Wenner method of impedance measurement for health evaluation of reinforced concrete structures”, Construction and Building Materials, 197, pp. 576–586, 2019. 13 [17] S. S. Pathak, M. D. Blanton, S. K. Mendon, and J. W. Rawlins, “Investigation on dual corrosion performance of magnesium-rich primer for aluminum alloys under salt spray test (ASTM B117) and natural exposure”, Corrosion Science, 52, pp. 1453–1463, 2010. [18] M. Zhao, P. Schmutz, S. Brunner, M. Liu, G. Song, and A. Atrens, “An exploratory study of the corrosion of Mg alloys during interrupted salt spray testing”, Corrosion Science, 51, pp. 1277–1292, 2009. 14 Apendices Table 1 Salt spray test results for rail clip without Nano-coating Salt concentration: 5±1 weight percent of NaCl + distilled water Temperature: 35±2 °C Spraying pressure: 0.83-1.24 bar Solution pH: 6.5-7.2 Cleaning method after the test: washing with water Spray time: 1000h Collected volume: 1-2 mL/h Number: 1 Test results Spray time(h) Observations 24 Rust was observed at about 10% of the rail clip surface 48 Rust increased to about 30% of the rail clip surface 72 Rust increased to about 50% of the rail clip surface 96 Rust increased to about 60% of the rail clip surface 120 Rust increased to about 80% of the rail clip surface 144 Rust increased to about 100% of the rail clip surface 168 No significant change than before 192 No significant change than before 216 No significant change than before 240 No significant change than before 264 No significant change than before 288 No significant change than before 312 No significant change than before 336 No significant change than before 360 No significant change than before 384 No significant change than before 408 No significant change than before 432 No significant change than before 456 No significant change than before 480 No significant change than before 504 No significant change than before 528 No significant change than before 552 No significant change than before 576 No significant change than before 600 No significant change than before 624 No significant change than before 648 No significant change than before 672 No significant change than before 696 No significant change than before 720 No significant change than before 744 No significant change than before 768 No significant change than before 792 No significant change than before 816 No significant change than before 840 No significant change than before 864 No significant change than before 888 No significant change than before 912 No significant change than before 936 No significant change than before 960 No significant change than before 984 No significant change than before 1000 No significant change than before 15 Table 2 Salt spray test results for rail clip with Nano-coating Salt concentration: 5±1 weight percent of NaCl + distilled water Temperature: 35±2 °C Spraying pressure: 0.83-1.24 bar Solution pH: 6.5-7.2 Cleaning method after the test: washing with water Spray time: 1000h Collected volume: 1-2 mL/h Number: 1 Test results Spray time(h) Observations 24 The rail clip was completely sound 48 The rail clip was completely sound 72 The rail clip was completely sound 96 The rail clip was completely sound 120 The rail clip was completely sound 144 The rail clip was completely sound 168 The rail clip was completely sound 192 The rail clip was completely sound 216 The rail clip was completely sound 240 The rail clip was completely sound 264 The rail clip was completely sound 288 Blisters were observed at the surface of the rail clip 312 The size and number of blisters increased 336 The size and number of blisters increased 360 The size and number of blisters increased 384 The size and number of blisters increased 408 The size and number of blisters increased 432 The size and number of blisters increased 456 No significant change than before 480 No significant change than before 504 No significant change than before 528 No significant change than before 552 No significant change than before 576 No significant change than before 600 No significant change than before 624 No significant change than before 648 No significant change than before 672 No significant change than before 696 No significant change than before 720 No significant change than before 744 No significant change than before 768 No significant change than before 792 No significant change than before 816 No significant change than before 840 No significant change than before 864 No significant change than before 888 No significant change than before 912 No significant change than before 936 No significant change than before 960 No significant change than before 984 No significant change than before 1000 No significant change than before 16 Table 3 Salt spray test results for screw spike without Nano-coating Salt concentration: 5±1 weight percent of NaCl + distilled water Temperature: 35±2 °C Spraying pressure: 0.83-1.24 bar Solution pH: 6.5-7.2 Cleaning method after the test: washing with water Spray time: 1000h Collected volume: 1-2 mL/h Number: 1 Test results Spray time(h) Observations 24 Rust was observed at about 20% of the screw spike surface 48 Rust increased to about 30% of the screw spike surface 72 Rust increased to about 40% of the screw spike surface 96 Rust increased to about 50% of the screw spike surface 120 Rust increased to about 60% of the screw spike surface 144 Rust increased to about 80% of the screw spike surface 168 Rust increased to about 100% of the screw spike surface 192 No significant change than before 216 No significant change than before 240 No significant change than before 264 No significant change than before 288 No significant change than before 312 No significant change than before 336 No significant change than before 360 No significant change than before 384 No significant change than before 408 No significant change than before 432 No significant change than before 456 No significant change than before 480 No significant change than before 504 No significant change than before 528 No significant change than before 552 No significant change than before 576 No significant change than before 600 No significant change than before 624 No significant change than before 648 No significant change than before 672 No significant change than before 696 No significant change than before 720 No significant change than before 744 No significant change than before 768 No significant change than before 792 No significant change than before 816 No significant change than before 840 No significant change than before 864 No significant change than before 888 No significant change than before 912 No significant change than before 936 No significant change than before 960 No significant change than before 984 No significant change than before 1000 No significant change than before 17 Table 4 Salt spray test results for screw spike with Nano-coating Salt concentration: 5±1 weight percent of NaCl + distilled water Temperature: 35±2 °C Spraying pressure: 0.83-1.24 bar Solution pH: 6.5-7.2 Cleaning method after the test: washing with water Spray time: 1000h Collected volume: 1-2 mL/h Number: 1 Test results Spray time(h) Observations 24 The screw spike was completely sound 48 The screw spike was completely sound 72 The screw spike was completely sound 96 The screw spike was completely sound 120 The screw spike was completely sound 144 The screw spike was completely sound 168 The screw spike was completely sound 192 The screw spike was completely sound 216 The screw spike was completely sound 240 The screw spike was completely sound 264 The screw spike was completely sound 288 The screw spike was completely sound 312 The screw spike was completely sound 336 The screw spike was completely sound 360 The screw spike was completely sound 384 The screw spike was completely sound 408 The screw spike was completely sound 432 The screw spike was completely sound 456 The screw spike was completely sound 480 The screw spike was completely sound 504 The screw spike was completely sound 528 The screw spike was completely sound 552 The screw spike was completely sound 576 The screw spike was completely sound 600 The screw spike was completely sound 624 The screw spike was completely sound 648 The screw spike was completely sound 672 The screw spike was completely sound 696 The screw spike was completely sound 720 The screw spike was completely sound 744 The screw spike was completely sound 768 The screw spike was completely sound 792 The screw spike was completely sound 816 The screw spike was completely sound 840 The screw spike was completely sound 864 The screw spike was completely sound 888 The screw spike was completely sound 912 The screw spike was completely sound 936 The screw spike was completely sound 960 The screw spike was completely sound 984 The screw spike was completely sound 1000 The screw spike was completely sound 18