1. A study on Supercritical Electrolytic Polishing Process for Stainless steel substrates Jau-Kai Wang 1 ※, Yan-Ru Wang 2 and Yan-Ru Wang 3 1.Department of Applied Chemistry & Material Science, Fooyin University, 151 Chin-Hsueh Rd, Ta-Liao Hsiang, Kaohsiung City, 831 Taiwan, R.O.C. 2. Department of Computer Science, National Chiao Tung University,1001 University Road, Hsinchu, Taiwan 300, ROC 3. Department of Chemistry, National Sun Yat-Sen University, No. 70, Lienhai Rd., Kaohsiung 80424, Taiwan, ROC Abstract The polishing technique is an important surface treatment method used in both conventional and electronic industry. Traditionally, there are three main skills included (1) mechanic polishing (2) electrolytic polishing (3) chemical polishing. However, all of them could not deal with complex parts with higher aspect ratio and serious environmental problem with labor cost. In this work, we have explored a new polishing method which applies principles of electro-chemistry and electro-physics to treat the surface of stainless substrate under the supercritical carbon dioxide fluid. It used to get rid of oxides on it and to increase its smoothness as well as brightness. The various kinds of golf head were selected as the investigated system. The roughness of sample can be upgraded to nano-metered size (~200nm) and the it’s brightness of mirror also be obtained (reflectivity > 95%). It is highlighted that the new supercritical polishing method is a green process without polluting environments and it is suitable to complex work pieces and simple operation with high efficiency. Keywords: polishing, gold head, brightness, roughness 3. Results and Discussion 1.Introduction 3.Experimental The polishing technique is an important surface treatment method used in both conventional and electronic industry. Traditionally, there are three main skills included (1) mechanic polishing (2) electrolytic polishing (3) chemical polishing. However, all of them could not deal with complex parts with higher aspect ratio and serious environmental problem with labor cost [2]. In this work, we have explored a new polishing method which applies principles of electro-chemistry and electro-physics to treat the surface of stainless substrate under the supercritical carbon dioxide fluid, to get rid of oxides on it and to increase its smoothness as well as brightness. The various kinds of golf head were selected as the investigated system. The roughness of sample can be upgraded to nano-metered size (~200nm) and the its brightness of mirror also be obtained (reflectivity > 95%). The polishing waste can be reused in another field because it is nano-scaled ferric oxide powder. It is highlighted that the new supercritical polishing method is a green process without polluting environments and it is suitable to complex work pieces and simple operation with high efficiency. The characteristic of supercritical polishing are list in Table 1 [2]. Table 1 Comparison between methods of polishing  In this study we have develop a new method of polishing for stainless steel through supercritical carbon dioxide fluid without pollution problem.  The chemical bath composition is natural without hurt to environment and stable after long-term operation.  Choosing reasonable treatment conditions, ideal surface reflectivity(>90%) and low roughness(~0.01  m) can be attained through supercritical polishing process for industry application.  It is also highlighted that side product of polishing ash was a micmeter-sized Fe 2 O 3 particles and might explored for another application in the future work.  This work has been approved by R.O.C Patent. 5.Conclusion 1. J-K Wang, ROC Patent 538146 (2005). 2. J-K Wang, ROC Patent I404826 (2013). ． 3. T. Fritz, et. al., Electrochim. Acta, 47, 55(2001). 4. G. Nelissen, et. al., Galvanotechnik, 4, 970(2000). 5. D. de Kubber, et. al., Electrochim Acta, 47, 91(2001). 6. S. C. Hung, et. al., Microelectro. Rel., 41, 677(2001). 7. P. A. Jacquet, Nature, 135, 1976(1935). 8. Jacquet, P.A., Trans. Electrochem Soc, 69, 629, (1936) 9. W. C. Elmore, J. Appl. Phys., 10, 724(1939) 10. T. P. Hoar and J. A. S. Mowat, Nature, 165, 64(1950) Reference Figure 7 Polishing effect on Hardness. Figure 8 Polishing effect on surface removal. A high-pressure experimental apparatus were fabricated by ourselves and its outline was shown in Figure 2 [2], used for supercritical polishing. The working tube was made of stainless steel 316 with an internal diameter of 20.15cm and a length of 21.5cm. A typical polishing reaction was performed in a constantly agitated ternary system of sc-CO 2, the chemical solution and a surfactant. The green chemical solution and the surfactant were both put in a high-pressure cell. CO 2 was introduced to the high-pressure cell using a pump and pressurized to a predetermined pressure. The ternary system was then constantly agitated at a speed of 400 rpm under a desirable constant temperature. The electroplating reaction commenced after 30 min of agitation, and the resistances in the reaction systems were simultaneously measured. The entire electroplating reaction for each sample was carried out for the designed time at 300.0 V. The optical microscopic images of gold deposited film were obtained using a High -Resolution Scanning Electron Microscope & Energy Dispersive Spectrometer, model number Hitachi S-4700I of Japan. Corrosion current values were measured using an Potentiostatic Anodic Polarization Measurements by Tafel equation. 3.1 supercritical polishing for golf head 3. 2 Performance of supercritical polishing Fig. 2. An experimental apparatus was used for a batch electroplating reaction with the emulsion of a CO 2, surfactant and the electroplating solution. The apparatus is labeled as follows: (a) CO 2 cylinder; (b) cooler; (c) high pressure pump; (d) temperature-controlled air bath; (e) reactor with magnetic stirrer; (g) trap; (f) programmable power supply; (h) gas meter; BPR: back-pressure regulator; PI: pressurei ndicator; TI: temperature indicator; V: valve. Chemical polishingElectro-polishingSupercritical polishing Solution priceexpensive cheap poisonserious none agingNot reuse recycle wastelarge less pollutionserious none pretreatmenttedious none postreatmentnecessary none levelingpoorbetter excellent brightnessgood excellent Complex partssuitable automationsuitable operationdifficult easy rateslowquickly Hardnesstrace positive Electric field, volts Polishing current, A Va Vb Vc Electro- polishing Vd Ve Vc Supercritical polishing Electro-chemical polishing goes on at section ab of the Curve. While polishing, the voltage is low, a film with high resistance is formed from the dissolved substance on the surface of the anode. Because on the surface of the anode electric current is uneven, the current density at the crowning region is greater than the concave region, so the metal at the crowning region is dissolved faster than that at concave region to get the coarse surface to be even.[3-7] Supercritical polishing goes on at section de of the Curve Using the vapor-gas layer, produced near the surface of the product, the treated surface is separated from electrolyte and intensive physical, chemical and elector-chemical reactions take place between the product and the vapor of the electrolyte. [9-10] 2.Theorectical Consideration Figure 3 Polishing effect on SUS 304 golf head. Figure 4 Polishing effect on SUS 17-4golf head. Figure 1 Polishing curve of I-V Figure 5 Polishing effect on roughness. Figure 6 Polishing effect on brightness.