CHARACTERISATION OF HONEYCOMB STRUCTURE.pptx

honey comb structure

1. Abstract Honeycomb structures are natural or man-made structures that have the geometry of a honeycomb to allow the minimization of the amount of used material to reach minimal weight and minimal material cost. The geometry of honeycomb structures can vary widely but the common feature of all such structures is an array of hollow cells formed between thin vertical walls. The main requirement for stainless steels is that they should be corrosion resistant for a specified application or environment. The selection of a particular "type" and "grade" of stainless steel must initially meet the corrosion resistance requirements. Additional mechanical or physical properties may also need to be considered to achieve the overall service performance requirements. In order to increase its wear resistance and hydrophobic nature a layer of protective coating is also applied which in turn acts as a barrier between base metal. The aim is to provide increased life for the component and to make it less expensive.  

2. Honeycomb  materials are widely used where flat or slightly curved surfaces are needed and their high specific strength is valuable . Its hexagonal shape of core makes optimum mechanical properties and is able to carry shear loads at much lower weight than foams or other core types. Advantages : Provides high strength  less metal is needed to produce than solid products  resistance to compression is also high Exceptional strength to weight ratio Applications : Water desalination plants Marine applications Off shore structures

3. Applications: Separating walls of water desalination plants which aims to provide potable water from brackish and recycled water Splash zone is the area immediately above and below the mean water level. It has long been a major concern to both design and corrosion Tides cause the water level to rise and fall, alternately wetting and drying exposed metal surfaces, such as offshore oil and gas platform legs and risers Seawater Bridge columns as shown in fig below immersed portion which is under water gets eroded over a period of time due to splashing of water simultaneously The exposure to the harsh marine environment is one major challenge for the construction and duration of offshore structures, which are mainly made of steel

4. Objectives to be noted before considering material are Corrosion strength Wear resistance Hardness To be economical and satisfying above all objectives, Stainless steel is considered as best material to be used for outer covering Stainless steel  is a  metal  alloy, made up of  steel  mixed with elements such as chromium, nickel, molybdenum, silicon, aluminum, and carbon The Three Main Categories of Stainless Steel Austenitic Stainless Steels Ferritic Stainless Steels Martensitic Stainless Steels

5. Austenitic Stainless Steels These are the most frequently used types of stainless steels. Austenitic stainless steels tend to have a high chromium content compared to other steel alloys, giving them a higher resistance to corrosion Common Types of Austenitic Stainless Steels Grade 304 Stainless Steel The   grade 304 stainless steel is noteworthy for its high tensile strength. Like most stainless steels, grade 304 has a high maximum operating temperature (about 870˚C). This combination of high tensile strength, temperature resistance, and corrosion resistance makes grade 304 stainless steel ideal for a wide variety of applications. Grade 316 Stainless Steel The grade 316 stainless steel  has a high tensile strength and a maximum use temperature of around 800˚C (1,472˚F). While having a lower tensile strength and temperature tolerance than grade 304 stainless steel, grade 316 stainless has a better resistance to chlorides (like salt) than 304 alloy does. This makes it a preferred choice for any application involving exposure to salt or other chlorides .

6. Grade Fe Cr Ni Mo Mn Si C SS304 66.52 17.7 8.04 0.29 1.08 0.42 0.07 SS316 63.86 16.3 10.2 2.08 1.5 0.445 0.02 Chemical composition Like 304 stainless steel, 316 contains chromium and nickel. However, it also has molybdenum (2% to 3%) as part of its makeup. That small addition of atomic number 42 lends some unique characteristics to 316 stainless steel i.e , Superior Corrosion and Chlorine Resistance 316 stainless has a stronger resistance to various chemical agents that might damage or corrode 304 stainless steel However, 316 stainless steel also excels at resisting brine. That makes it ideal for working in marine applications

7. In marine applications , The most form of corrosion can occur in Stainless steels is Pitting corrosion: The passive layer on stainless steel can be attacked by certain chemical species. The chloride ion Cl - is the most common of these and is found in everyday materials such as salt and bleach. Pitting corrosion is avoided by making sure that stainless steel does not come into prolonged contact with harmful chemicals or by choosing a grade of steel which is more resistant to attack In order to overcome this SS316 is chosen which is chloride ion resistant

8. Methodology: On a CNC laser cutter, the laser cutting head is moved over the metal plate in the shape of the desired part, thus cutting the part out of the plate. A capacitive height control system maintains a very accurate distance between the end of the nozzle and the plate that is being cut. This distance is important, because it determines where the focal point is relative to the surface of the plate. Cut quality can be affected by raising or lowering the focal point from just above the surface of the plate, at the surface, or just below the surface When cutting stainless steel or aluminum, the laser beam simply melts the material, and high pressure nitrogen is used to blow the molten metal out of the kerf .

9. Specification of specimen:

10. Need for Protective Coating: To protect structure from corrosion and wear resistance various types of coatings are under consideration and According to the availability in this situation Nickel coating: Electro nickel plating, also known as nickel electroplating or nickel electro-deposition, is becoming an increasingly popular process for a variety of different manufacturing applications. Electro nickel plating is a process that uses an electrical current to coat a conductive material, typically made of metal, with a thin layer of nickel. Other metals used for electroplating include stainless steel Nickel Features: Increases the hardness and the durability of mechanical parts and tools Scratch-resistant and abrasion resistant Advantages: Unbeatable surface deactivation Corrosion protection Improved ductility Resistance to wear

11. Electro deposition of Nickel: Electrodeposits are formed by the action of an electric current passing in an electrochemical cell, a device that consists of two conductive or semi-conducting electrodes immersed in an electrolyte. The electrodes are called the working electrode (cathode), consisting of the object where electrode position is planned, and the counter-electrode (anode), necessary to complete the electrical circuit. Electrolytes for electro deposition are usually aqueous solutions containing positive and negative ions, prepared by dissolving metal salts. The electric current that flows between the two conductive electrodes in the presence of an external voltage is because of the motion of charged species, via migration and diffusion, towards the surfaces of the polarized electrodes. At the surface of the electrodes, the conduction mechanism must change from ionic to electronic, an interface process mediated by the occurrence of electrochemical reactions that promote the reduction or the oxidation of the ionic species. Materials required Distilled vinegar ( 5% acidity or higher) used as an electrolyte Salt ( to improve reaction) Large jar for specimen dipping Connecting wires 6V battery

12. LITERATURE: Muntazir Abbas Mahmood Shafiee [1] To analyse the effect of marine environmental conditions on corrosion-based degradation of steel structures. It also highlighted the prognostic models on marine corrosion phenomenon and its impact on the reliability, health assessment, inspection intervals and overall maintenance strategy selection of assets. Due to significant variability of environmental factors, the corrosion in marine steel structures shows a great variation in different immersion zones. Hence, it is necessary to update corrosion models or their parameters according to the metal loss in different immersion zones, phases of corrosion, compositions of seawater, geographical regions. Tristan Senga Kiesse , Stephanie Bonnet , Ouali Amiri , Anne Ventura[2] The chloride-induced steel corrosion is one of the main causes of deterioration for reinforced concrete structures exposed to marine environments. The chloride ingress into reinforced concrete structures is even more complex since it depends on random parameters linked to transport and chemical properties of materials, which results in variability of corrosion initiation. Siyun Zou , Xianliang Zhou, Youhai Rao , Xiaozhen Hua , Xia Cu[3] The corrosion behaviour of the electrodes Ni-P plating is investigated and compared with non-coated SiCp /Al composites in 0.05 M NaCl solution. The SEM results showed that: With the increase of nickel plating time, the nickel and phosphorus layer deposited on the surface of composite material is becoming denser and continuous, and the plating layer is thicker and thicker. The 60-min electroless Ni-P layer on the SiCp /Al composites surface presents a good uniformity, no pores and cracks at the layer, and the growth mode is layered. The EDS results showed that the thickness of 60-min electroless Ni-P layer is about 15 μm with a good bonding power. It can be seen from the XRD spectrum that 60-min coating film shows an amorphous structure. A Madhan Kumar[6] Modify the surface of steel by hybrid  silane  coatings using dip- coating.Study the effect of dipping time and cycles on coating morphology and corrosion.10-minutes and 3-dipping cycles gives the best corrosion resistance.Correlation between surface  wettability  and corrosion resistance established.

13. S.Atashin M.Pakashir A.Yazdani [4] The corrosion rate of the austenitic stainless steel AISI 316, under the synergistic effect of environmental factors, has been assessed via potentiodynamic polarization scan. Salinity, velocity, pH and temperature are the factors that induce effects on the corrosion rate of the considered metal. Quan - titative analysis is applied using the full two-level factorial experimental design method. This analysis calculates the contribution value of each parameter in changing the quantity of average corrosion rate in both individual and synergistic cases Zhanwen Wang, Lida Shen , Wei Jiang [5] a simple, flexible method to fabricate the super hydrophobic nickel coatings by scanning electro deposition was proposed. By changing the parameter of current densities, the morphology, microstructure, chemical composition, wettability , and stability of the samples were studied. The results showed that the clusters with hierarchical structures and the chemical composition were important in the formation of super-hydro- phobic surface Wei- Ja Shong Chien-Kuo Liu Szu -Han Wu [6] The development of duplex steels in recent years has resulted in a number of grades with a better balance between austenite and ferrite and far better weldability than the old type. The corrosion resistance varies, depending on alloy content, but in general terms; duplex steels represent a span ranging from 316L to 6Mo austenitic grades. One of the lowest alloyed grades, S32304 (SAF 2304Ô) has the same resistance to pitting and crevice corrosion as 316L, superior resistance to stress corrosion cracking, while the resistance to uniform corrosion depends on type of environment in which it is used.

14. Method of testing: To analyze corrosion behavior: Salt spray (or salt fog) test  is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings. This accelerated laboratory test was invented at the beginning of the 20th century. It provides a controlled corrosive environment and has been used to produce relative corrosion-resistance information for specimens of metals and coated metals exposed in a test chamber. The classical salt spray (fog) test ASTM B117 consists of atomizing a salt solution into uniform droplets on specimens supported or suspended between 15-30° from the vertical. The salt solution is a solution of 5% (in weight) of NaCl , (more than sea water, which is only 1.8% to max 3%). The exposure zone of the salt spray chamber is maintained at 35°C. Testing Equipment :

15. Potentiodynamic polarisation test: A software based PAR weld electrochemical system of the GILL AC unit was used to conduct the potentiodynamic polarization tests for studying the pitting corrosion behavior of coated samples. A saturated calomel electrode (SCE) and carbon electrode were used as reference and auxiliary electrodes respectively. All the experiments were conducted in aerated 3.5% NaCl solution with pH adjusted to 10 by adding potassium hydroxide. The potential scan was carried out at 0.166 mV/sec with the initial potential of -0.25 V (OC) SCE to the final pitting potential. The exposure area for these experiments was 1 cm 2 and current has been inducted into the electrolyte. The potential at which anodic and cathodic current is equal was considered to be the corrosion potential ( E corr ). Through the obtained E corr values the pitting corrosion resistance of the coatings has been determined.

16. Micro structural analysis: Basic activities that are performed before evaluating of the microstructures of coatings are sectioning, cleaning and mounting, grinding, polishing, optical microscopy image analysis. Optical Microscope Prior to encapsulation of the specimen in the mounting material, the size of the specimen is decreased by sectioning the samples in a standard method with abrasive cutting using rotating wheels. After sectioning, the samples are cleaned with ultrasonic cleaning. In order to have grip of the specimen they are then mounted by using cold mounting process, prepared by mixing the resin (acrylic) with hardener. This type of mounting is preferred for specimens ae these are resistant to most of the chemicals with short curing times and negligible shrinkage.

17. Vickers Hardness test The unit of hardness acquired by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). As the Vickers test can be used for all metals and has one of the widest scales among hardness tests, the basic properties of coatings i.e , the micro hardness of coated samples at their cross section was measured using a calibrated Vickers micro indentation hardness intender. It was done under a test load of 300 grams, dwell time 15s, indenter speed of 60µm/sec, and the angle between two faces is maintained as 136 . The hardness number determined by the load applied over the surface area of indentation .The reported values are averages of 6 measurements. Formula to find Vicker’s Hardness Value, HV = 2 F sin(Ө/2) D 2     Where: F = Applied load in kgf D = Mean diagonal of the indentation (mm) D = (d 1 +d 2 )/2 Ө = Angle between opposite faces of diamond = 136 ͦ

18. Results and Discussion Corrosion analysis: The corrosive behaviour of coatings is evaluated by measuring corrosion resistance of coatings. The polarisation curves of the deposited coatings are obtained by using Gill AC Electrochemical system as showed in the fig 4.1. The potentiodynamic polarisation curves were measured with a scan rate of 1mV/s and When the current is inducted into the electrolyte, it is observed that up to certain extent there is no corrosion of the coating but after attaining a certain potential the coatings are started to corrode where anodic and cathode potentials are equal for which E corr values are observed and the analysis is as presented below. specimen E corr ( mV) I corr ( mA /cm 2 ) Uncoated -371.28 0.000433 Coated -285.59 0.0001394 It can be seen in the table that the I corr values of uncoated specimen is higher than the coated samples which indicates lower transportation of ions and charges at coating interface leads to better corrosion protection of the base material. Furthermore, the corrosion rate is directly proportional to the I corr Therefore, lower the I corr value higher will be the corrosion resistance. The rate of conductivity decreases as we observe there is a steep decrease in I corr .

19. Micro structural Evaluation: Micro structural characterisation of the coatings is studied and it strongly influences the physical properties such as bonding between the substrate and coating, hardness, toughness, ductility, high/low temperature behaviour, wear resistance, corrosion resistance and so on. This in turn depends on the application of these materials in industrial practice. Base stainless steel microstructure Nickel coated specimen micro structure Observation from structure: Grain density increases The presence of those micro defects gradually reduced on the surface Micro cracks and pores nearly disappeared on the surface  

20. Micro hardness The results obtained from the experimentation of mean micro hardness values for the Ni coating is as shown below. The micro hardness of the base and coating specimen is as follows respectively. HV = 2 F sinӨ /2 D 2 Applied load = 10 N Angle between opposite faces of diamond = 136 Hardness of Base : Hardness of Coating : d 1 =0.07mm d 1 = 0.049mm d 2 =0.13mm d 2 = 0.065mm D= 0.1mm D= 0.057mm HV = (2 * 1.02 * 0.927183)/ 0.1 2 HV = (2 * 1.02 * 0.927183)/0.057 2 HV = 197.84 HV = 580.0252 Hardness base =197.84 HV Coating hardness= 580HV   From the values, It observes that all the blending coatings are exhibited superior micro hardness compared to unblended coatings. The presence of Nickel in the microstructure is responsible for higher micro hardness of coatings. Among the both basic uncoated and coated specimens, Ni coating exhibited higher hardness than the uncoated specimen.

21. CONCLUSION In the first phase of work, To increase impact strength and hardness honeycomb structure is preferred by considering its inherent properties on the base plate by laser cutting process. In order to increase corrosion resistance, Electrolysis of Nickel plating is successfully employed for depositing of coating. Initially mechanical properties like micro hardness, micro structural evaluations of these are evaluated and corrosion behaviour is also studied. The micro hardness for the coating specimen is found to be far superior compared to non-coated specimen. High hardness of the coatings is considered to be advantageous towards the improvement of wear resistance. Micro structural examination and evaluation of properties when compared both showed that the coated specimen is well packed in and without much defects and fractures Corrosion behaviour for the coating specimen and non coated specimen is conducted in aerated 3.5% NaCl solution and it is showed that Nickel coated specimen showed excellent corrosion resistance.

22. REFERENCES H.S. Khatak , and R. Baldev , Corrosion of Austenitic Stainless Steels: Mechanism, Mitigation and Monitoring . ASM International. Narosa PublishingHouse : (2002). Liyakath Ahmed Sheik, and Sunil Kumar Tamida , Studies on galvanic corrosion of tri-metallic joint of steels in sodium chloride solution INTERNATIONAL STAINLESS STEEL FORUM “The salt spray test and its use in ranking stainless steels” A technical guide to salt spray test and its interpretation with stainless steels S. G. Croll , M. Buratto , T. Calzone, C. Gu , D. Robinson, S. M. Smith, V. Upadhyay , B. D. Keil , “Changes during Weathering of Polyurethane Water Pipeline Coatings,” American Society of Civil Engineers, Pipelines Proceedings, Kansas City, Missouri, July 17 - 20th , 2016 A Hussain , Abdul jaleel , Investigation of marine environmental behavior Environment related behavior of coal tar epoxy painting on tubular steel paintings Nicole overman , Kenneth Ross and Christopher Smith, “Microstructure hardness and cavitation erosion resistance of different cold spray coatings on stainless steel 316 for hydropower applications” R N Choudary B P Malik “Mechanical and anticorrosive properties of non toxic coal tar epoxy coating” D. Bruce, and Craig, Selection Guidelines for Corrosion Resistant Alloys in the Oil and Gas Industry Materials Selection for the Oil and Gas Industry (October 2009). R. Nishimura, A. Sulaiman , and Y. Maeda, Stress corrosion cracking susceptibility of sensitized type 316 stainless steel in sulphuric acid solution J. Corrosion Science. 45:465-484 (2003). S.Karthick S.Prasanna Raj Yadav C.Joel K.Senthilnathan Ramya Suresh S.Muthukumaran A straightforward trail study on analysis of thickness variation of black nickel coating on stainless steel surface

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