R.Sasidharan , S.Rajendra Boopathy, S.R. Koteswara Rao and B.Ganesamoorthi
Keywords: Liters per minute, Erosion corrosion, Tungsten inert gas welding, Taguchi method
Abstract:
In this study, the parameters for obtaining maximum erosion corrosion behaviour(weight loss) of the Gas tungsten arc (GTAW or TIG) welded duplex stainless steel were delivered. Essentially, the erosion corrosion behaviour is determined by several quality characteristics, for instance, the pH value, % mixture of sand in water (slurry) and slurry flow rate in Liters per minute (LPM). To look at these material removal rate(weight loss) in the selection of process parameters, the Taguchi method was adopted to evaluate the effect of each erosion corrosion parameter and then to define the process parameters for the maximum erosion corrosion behaviour. Experimental results were offered to establish the proposed approach.
Because you are not logged-in to the journal, it is now our policy to display a 'text-only' version of the preprint. This version is obtained by extracting the text from the PDF or HTML file, and it is not guaranteed that the text will be a true image of the text of the paper. The text-only version is intended to act as a reference for search engines when they index the site, and it is not designed to be read by humans!
If you wish to view the human-readable version of the preprint, then please Register (if you have not already done so) and Login. Registration is completely free.
ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Study on Erosion Corrosion behaviour of Gas Tungsten A r c Welded Duplex Stainless Steel using Taguchi Technique. R.Sasidharan1* , S.Rajendra Boopathy2, S.R. Koteswara Rao1, B.Ganesamoorthi2 1 *Department of Mechanical Engineering, Tagore Engineering College, Chennai, India. 2 Department of Mechanical Engineering, Anna university, Chennai, India. * Corresponding Author (sasienggdes@gmail.com) Abstract In this study, the parameters for obtaining maximum erosion corrosion behaviour(weight loss) of the Gas tungsten arc (GTAW or TIG) welded duplex stainless steel were delivered. Essentially, the erosion corrosion behaviour is determined by several quality characteristics, for instance, the pH value, % mixture of sand in water (slurry) and slurry flow rate in Liters per minute (LPM). To look at these material removal rate(weight loss) in the selection of process parameters, the Taguchi method was adopted to evaluate the effect of each erosion corrosion parameter and then to define the process parameters for the maximum erosion corrosion behaviour. Experimental results were offered to establish the proposed approach. Keywords: Liters per minute, Erosion corrosion, Tungsten inert gas welding, Taguchi method © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Introduction Tungsten inert gas (TIG) welding is an important welding process, which uses a non consumable tungsten electrode coupled with inert gas for arc shielding. It is most frequently used for welding hard-to-weld metals such as stainless steel [1]. Basically, solid particle combined with liquid droplet erosion are surface removal processes caused by encroachment of solid particles carried in moving fluid stream in opposition to the airfoil. Unremarkably, the desired erosion corrosion process parameters are set based on experience or from a handbook. Corrosion is an omnipresent form of surface degradation, occurring in both natural systems and fabricated products. In machinery and materials handling equipment for industrial applications most component damage is induced by the impact of small solid particles entrained in a gasoline or liquid stream [2]. Such erosion of material surfaces occurs by a high strain rate extrusion, forging fracture mechanism that differs from other cases of wear processes such as abrasive wear and sliding wear [2,3]. The complexity of the erosion–corrosion phenomena is not just limited to the interaction between the various parameters affecting erosion corrosion. In order to see the total wear rate caused by the mixed consequence of erosion and corrosion, various rigs have been planned to evaluate this result. Amongst these rigs are slurry pot erosion tester[4–9],], Coriolis erosion tester [10–12] and rotating cylinder apparatus [13–15]. Nevertheless, this does not assure that the selected erosion corrosion process parameters can generate the optimal or close to optimal weight loss for that particular erosion corrosion machine and environment. In this report, the role of the Taguchi method to limit the erosion corrosion process parameters with the optimal weight loss is accounted. Taguchi method [16,17] is an organized application of design and analysis of experiments for the purpose of planning and improving product quality. In recent years,[18] the Taguchi method has become a potent instrument for improving output during research and evolution so that high quality products can be grown © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 rapidly at low cost. Basically, the erosion corrosion behaviour of the weld pool has been influenced by weight loss of the weld pool. However, the original Taguchi method has been projected to optimize a single quality characteristic. Therefore, Taguchi method is embraced in this paper to examine the outcome of each parameter on the erosion weight loss along the weld metal, and then to learn the parameters with the optimal erosion corrosion behaviour. Experimental results are also provided to illustrate the proposed approach. In the pursuit, the Taguchi method for optimizing individual quality characteristics of the erosion corrosion behaviour using TIG welding process is described in detail. In the end, the report concludes with a detailed summary of this work. Experimental Procedure The Taguchi method Optimization of process parameters is the foremost measure in the Taguchi method to attain high quality without increasing cost. This is because optimization of process parameters can increase quality characteristics and the optimal process parameters obtained from the Taguchi method are insensitive to the variation of environmental conditions and other noise factors. Commonly, the number of experimentations that have to be carried out becomes higher when the number of the process parameters increases. To carry out this undertaking, the Taguchi method uses a particular design of orthogonal arrays to examine the entire process parameter with a lower number of experiments only. In this study, Irrespective of the category of the quality characteristic, a larger S/N ratio corresponds to a better quality characteristic. Taguchi recommends the exercise of the loss function to evaluate the difference of the quality characteristic from the desired value. Overall loss function calculated for the corresponding weight loss. The value of the overall loss function is further translated into a signal-to-noise (S/N) ratio. The S/N ratio for each degree of process parameters © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 is calculated based on the S/N ratio analysis. Furthermore, a statistical analysis of variation (ANOVA) is performed to determine which process parameters are statistically significant. Finally, a confirmation experiment is performed to support the optimal process parameters obtained from the process parameter design. Tungsten Inert Gas Welding (TIG) The Material selected for the studies were Duplex Stainless steel plates (UNS32205) of thickness 6mm plates. The plates were roughly polished with silicon carbide paper and cleaned with acetone. Welds were made using Autogenous Gas Tungsten Arc Welding using Argon as shielding gas. A standard non-consumable thorated tungsten electrode was used for welding. The parameters used for producing the Tig weld are given in Table 1. In t he above cases, complete penetration bead on weld joint were produced by single pass. Mechanical and Corrosion Testing The Erosion corrosion test is held away in the typical Erosion testing machine. The test specimen is prepared in flat side perpendicular to the focal point of the discharge nozzle as shown in Fig. 3. Slurry is prepared using mixing up of water and abrasive mixture (50-70 mesh). The abrasive mixture contains the chemical composition of SiO2-99.76%, Al2O3-0.5%, Fe2o3, Potash and soda. slurry is prepared in the ratio of mixing water and abrasive sand by (i) 1liter of water : 0.1kg of abrasive sand = 10, (i) 1liter of water : 0.2kg of abrasive sand = 20, (i) 1liter of water : 0.3kg of abrasive sand = 30 (water : abrasive mixture). Each erosion corrosion test is carried out with a time span 6hr per test. Weld metal Ferrite content was measured using Fisher Ferritoscope, taking an average value of 10-15 measurements from different positions according to ASTM E1019 standards. Studies were done to reveal the microstructure in base and weld metal of DSS. To study the pitting corrosion resistance of 2205 DSS plates, potentiodynamic © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 polarization tests were served using a Software based PAR Basic electrochemical system. Saturated calomel electrode (SCE) and carbon electrode were used as reference and auxiliary electrodes respectively. The experiments were led in 0.5 Mole H2SO4 (49ml in one litter) + 0.5 Mole NaCl (17gm in one litter) solutions with pH adjusted to 4. The potential scan was performed out at 0.166 mV/sec with the initial potential of –0.25V (OC) SCE to final potential of pitting. The touch region for these experiments was 1 cm2. The Potential at which current increases considerably was considered as critical pitting potential (Epit). Specimens exhibiting comparatively more positive potential, (or less negative potentials) were regarded as those with better pitting corrosion resistance. Optimal selection of process parameters In this section, the use of the Taguchi method to find out the process parameters in the Erosion Corrosion behaviour of TIG welds(DSS) is reported step-by-step. Erosion corrosion behaviour with the best(maximum erosion) process parameters are determined and verified. Orthogonal array experiment In the present study, three three-level process parameters, i.e. Ph value, flow rate, and Slurry percentage of silica sand, are considered. The value of the erosion corrosion process parameter were listed in Table 2(a). There are thus 6 degrees of freedom owing to the three sets of three level erosion corrosion process parameters. The degrees of freedom for the orthogonal array should be greater than or at least equal to the process parameters. In this study, an L9 (33) orthogonal array which has 6 degrees of freedom was used. Nine experiments are required to learn the entire erosion corrosion parameter space when the L9 orthogonal array is used. The experimental design for the erosion corrosion process parameters using the L9 orthogonal array is shown in Table 3 and © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 the experimental results for the erosion corrosion behaviour using the L9 orthogonal array are shown in Table 2(b). Overall loss function and its S/N ratio In this study, quality of erosion corrosion behaviour of weight loss belongs to the higher the-better quality characteristic. The loss function of the larger-the-better quality characteristic can be expressed as = 1 1 (1) where Lij is the loss function of the ith quality characteristic in the jth experiment, and yij the experimental value of the ith quality characteristic in the jth experiment . As a outcome, quality characteristics corresponding to Ph value, flow rate and percentage of silica sand of the weight loss are obtained using Eq. (1). The overall loss function is further transformed into the S/N ratio. In the Taguchi method, the S/N ratio is used to find out the deviation of the quality characteristic from the desired value. The S/N ratio in the jth experiment can be expressed as = −10 log (2) The S/N ratio corresponding to the overall loss function is shown in Table 4. The effect of each erosion corrosion process parameter on the S/N ratio at different levels can be separated out because the experimental design is orthogonal shown in Table 5. & Fig. 1 shows the S/N ratio graph the larger is the S/N ratio, the better is the superiority(maximum erosion) characteristics for erosion corrosion behaviour Anova The aim of the ANOVA is to investigate which erosion corrosion process parameters significantly affect the quality characteristic. This is achieved by dividing the total variability of the S/N ratios, which is assessed by the total of the squared deviations © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 from the total mean of the S/N ratio, in contributions by each erosion corrosion process parameter and the error. The percentage contribution by each of the process parameter in the total sum of the squared deviations can be employed to assess the importance of the process parameter change on the quality characteristics. In summation, the F test named after Fisher [19] can also be applied to determine which welding process parameters have a substantial consequence on the quality characteristics. Usually, the alteration of the erosion corrosion process parameter has a substantial force on the quality characteristic when the F value is great Results of ANOVA (Table 6 & Fig. 2) indicate that Ph value, flow rate and percentage of silica sand are the significant erosion corrosion process parameters affecting the material removal(weight loss). The percentage contributions due to these process parameters are shown in Table 6. Based on the above discussion, the process parameters with the optimal erosion corrosion behaviour are Ph value at level 3, flow rate at level 3 and percentage of silica sand at level 3. Minitab 16 used for optimization of process parameter and perform ANOVA. Confirmation Test The final step is to verify the improvement of the material removal(weight loss) using the optimal level of the erosion corrosion process parameters. In order to verify the experimental conclusion, confirmation test was performed. The confirmation test was performed by setting the optimum condition of the three factors such as 10ph for ph value, 18l/min for flow rate and 30% of silica sand. The weight loss was found to be 0.51g in the confirmation test. The confirmation test results features the erosion corrosion behaviour are greatly improved through this study. Microstructure, hardness and Pitting corrosion tests The microstructures of Base metal and weld metal of Duplex Stainless steel are shown in Fig. 4(a&b). Duplex stainless steel (DSS) normally contains equal proportions of body-centered cubic ferrite (α) and face-centered cubic austenite ( γ). The ferrite contents of the Base metal and weld metals, measured © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 magnetically are given in Table 7. Vickers microhardness test survey were conducted across the weld using 0.5kg load.. The results are pictorially shown in Fig. 7. The weld center showed higher hardness compared to the base material. Dynamic polarization curves of base material and TIG weld is shown in Fig. 5 & 6. The pitting potential values point out the potential at which the onset of pitting takes place, and the greater values indicate better pitting corrosion resistance. Conclusion In this paper, the selection of the process parameters for erosion corrosion behaviour of duplex stainless steel TIG welding w ith the highe r weight loss has been reported. The Taguchi method is adopted to find out the larger-the-better quality characteristics (higher weight loss). Experimental results have shown that e f f e c t o f the ph value, % mixture of sand in water (slurry) and slurry flow rate in Liters per minute(LPM) on weight loss due to erosion corrosion behaviour of TIG welded duplex stainless steel, are identified using this approach. References [1] H.B. Cary, Modern Welding Technology, Prentice-Hall, Englewood Cliffs, NJ, 1989. [2] I. Finnie(1995), Some reflections on the past and future of erosion, Wear, 186–187(1995), pp.1–10. [3] A.V. Levy(1995), Solid Particle Erosion and Erosion–Corrosion of Materials, ASM International, Materials Park, OH. [4] T.J. Harvey, J.A. Wharton, R.J.K. Wood(2007), Development of synergy model for erosioncorrosion of carbon steel in a slurry pot, Tribol. Mater. Surf. Interfaces 1 (1), pp.33–47. [5] H.M. Clark, K.K. Wong(1995), Impact angle, particle energy and mass loss in erosion by dilute slurries,Wear 186–187, pp. 454–464. © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 [6] H.M. Clark(2002), Particle velocity and size effects in laboratory slurry erosion easurements OR. . . Do you knowwhat your particles are doing? Tribol. Int. pp.617–624. [7] H.M. Clark, R.B. Hartwich(2001), A re-examination of the ‘particle size’ effect in slurry erosion, Wear 248, pp.147–161. [8] H.M. Clark(1991), On the impact rate and impact energy of particles in a slurry pot erosion tester, Wear 147, pp.165–183. [9] H.M. Clark(1993), Specimen diameter, impact velocity, erosion rate and particle density in a slurry pot erosion tester, Wear 162–164, pp.669–678. [10] H.M. Clark, H.M. Hawthorne, Y. Xie(1999), Wear rates and specific energies of some ceramic, cermet and metallic coatings determined in the Coriolis erosion tester, Wear 233–235, pp.319–327. [11] H.M. Clark, J. Tuzson, K.K.Wong, Measurements of specific energies for erosive wear using a Coriolis erosion tester,Wear 241 (2000)pp. 1–9. [12] Y. Xie, H.M. Clark, H.M. Hawthorne(1999), Modelling slurry particle dynamics in the Coriolis erosion tester,Wear 225–229, pp. 405–416. [13] M.M. Stack, J.S. James, Q. Lu(2004), Erosion–corrosion of chromium steel in a rotating cylinder electrode system: some comments on particle size effects, Wear 256, 557–564. [14] M.M. Stack, H.W.Wang, Simplifying the erosion–corrosion mechanism map for erosion of thin coatings in aqueous slurries,Wear 233–235 (1999)pp. 542–551. [15] M.M. Stack, H.W. Wang, W.D. Munz(1999), Some thoughts on the construction of erosion– corrosion maps for PVD coated steels in aqueous environment, Surf. Coat. Technol. 113, pp.52–62. [16] Y.M. Zhang, R. Kovacevic, L. Li(1996), Characterization and real-time measurement of geometrical appearance of the weld pool, Int. J.Mach. Tools Manuf. 36 (7), pp.799–816. © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 [17] S.C. Juang, Y.S. Tarng, H.R. Lii(1998), A comparison between the back propagation and counter-propagation networks in the modeling of the TIG welding process, J. Mater. Process. Technol. 75, pp.54–62. [18] A. Bendell, J. Disney, W.A. Pridmore(1989), Taguchi Methods: Applications in World Industry, IFS Publications, UK. [19] R.A. Fisher(1925), Statistical Methods for Research Worker, Oliver & Boyd, London. Table 1 Parameters For Tig Welding S.no Parameter Tig welding 1 Material grade Duplex 2205 2 Material thickness 6mm Electrode size(non consumable tungsten 3.4 mm dia 3 electrode) 4 Current 250 amps 5 Welding machine type Tig welding © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Table 2(a) Volume 17, Preprint 23 submitted 23 April 2014 Process parameters (Erosion corrosion) and their levels Symbol Process parameter Unit A Ph value Ph 4 7 10 B Flow rate l/min 12 15 18 C Percentage of silica sand % 10 20 30 Table 2(b) Level 1 Level 2 Level 3 Experimental layout using an L9 orthogonal array EXPERIMENT PH VALUE FLOW RATE % OF SILICA SAND 1 1 1 1 2 1 2 2 3 1 3 3 4 2 1 2 5 2 2 3 6 2 3 1 7 3 1 3 8 3 2 1 9 3 3 2 Table 3 Experimental result for the erosion corrosion behaviour © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 EXPERIMENT PH VALUE FLOW RATE submitted 23 April 2014 % OF SILICA WEIGHT LOSS SAND 1 4 12 10 0.0039 2 4 15 20 0.1096 3 4 18 30 0.5068 4 7 12 20 0.0039 5 7 15 30 0.1746 6 7 18 10 0.2673 7 10 12 30 0.0708 8 10 15 10 0.0294 9 10 18 20 0.3086 Table 4 S/N ratio for the erosion corrosion behaviour EXPERIMENT S/N ratio Table 5 1 -48.1787 2 -19.2038 3 -5.9033 4 -48.1787 5 -15.1591 6 -11.4600 7 -22.9993 8 -30.6331 9 -10.2121 S/N ratio response table for the erosion corrosion behaviour © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Symbol Process parameter Level 1 Level 2 Level 3 A Ph value -24.429 -24.933 -21.281 B Flow rate -39.786 -21.665 -9.192 C Percentage of silica -30.091 -25.865 -14.687 (The optimum level of the factors are given in bold the highest value in the column) Table 6 Symbol Results of ANOVA for the erosion corrosion behaviour Process Degrees Sum of Mean parameter of square square F Percentage of freedom contribution A Ph value 2 0.008506 0.004253 5.93 3.69 B Flow rate 2 0.183884 0.091942 128.30 79.86 C Percentage 2 0.036408 0.018204 25.40 0.000717 15.83 of silica sand Error 2 0.001433 total 8 0.230231 0.62 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 Table 7 submitted 23 April 2014 % Ferrite & Pitting Corrosion properties of Base metal & DSS welds. Specimen % Ferrite Designation Pitting Potential E(pitt) mV Base metal 51 940 Tig weld 57 925 List of Figures Figure 1 Effect of ph value, flow rate and percentage of silica sand on S/N ratio. Figure 2 contribution of each factor on the performance statistics ( influential effects based on percentage of contribution ). Figure 3 Schematic diagram of Erosion corrosion Slurry jet machine Figure 4(a) Base material microstructure – α (BCC-Ferrite), γ (FCC-Austenite). Figure 4(b) Weld microstructure – TIG Welding Figure 5 Effects of Pitting Corrosion on base metal Figure 6 Effects of Pitting Corrosion on TIG weld metal Figure 7 Vickers Microhardness survey on TIG welds © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Main Effects Plot for SN ratios Data Means Ph value flow rate -10 Mean of SN ratios -20 -30 -40 4 7 10 percentage of silica sand 12 15 18 -10 -20 -30 -40 10 20 30 Signal-to-noise: Larger is better Figure 1 Percentage of contribution Ph value Flow rate Percentage of silica sand Error Figure 2 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Figure 3 Figure 4(a) © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Figure 4(b) Figure 5 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 17, Preprint 23 submitted 23 April 2014 Figure 6 T IG W E L D Vickers microhardness(0.5kg load) 285 280 275 270 265 260 -1 0 -5 0 5 10 D is t a n c e f r o m c e n t e r ( m m ) Figure 7 © 2014 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work.