| In the International Thermonuclear Experimental Reactor (ITER) project, tritium, as the nuclear fusion energy, can permeate through the metal tube resulting in the waste of energy and the environmental pollutio.Tritium permeation barrier needs to be built on the internal surface of tube. Aluminum rich coatings consisting of an outer Al2O3 layer and inner Fe-Al layer are identified as a major candidate, because of high permeation reduction factor (PRF), good thermal property, and so on. But how to prepare a tritium permeation barrier on the surface of internal tube is still a key technical problem to be resolved.Based on this engineering application and a new approach proposed previously to prepare Fe-Al alloy layer on stainless steel by Al electrodeposition in room temperature ionic liquid, this research aims to prepare tritium permeation barrier on the internal surface of tubes. Thereby, investigations on the electroplating Al on the internal surface of the stainless steel tube were carried out. The influence factors of electroplating Al on the internal tube were investigated. The adhesion between coating and substrate was judged by scratching test, and the metallurgical features of coated samples were studied by means of optical microscope (OM) and scanning electron microscope (SEM).Firstly, based on reviewing the current researches on the device for inner tube electroplating, we designed and manufactured the device which can be used for electroplating Al on the internal tube in ionic liquids. The power for the circulation of ionic liquids in this system was provided by a peristaltic pump, of which the flow rate was quantificationally determined. The minimum pump flow rate at range of 0.077-0.436 L/min was determined by flow calculation. Tubing with a PTFE film on the internal surface was chosen to be the tubing for the transportation of ionic liquids. A container was designed and manufactured for the reservation of ionic liquids in atmospheric environment. Stainless steel double ferrule was used as the connection to be plated tube and tubing. By using this device, electroplating of Ni in aqueous solution was successfully performed on the internal surface of a Cu tube in atmosphere condition.Considering that the electroplating on Cu are easier and the color contrast of Cu and Al are more obvious, electroplating of Al in aluminum chloride-1ethyl-3-metheylimidazolium chloride (AlCl3-EMIC) ionic liquid on the internal surface of Cu was first carried out using the designed device. The results showed that the connector made of stainless steel was dissolved into the ionic liquid prior to the dissolution of Al anodes. In addition, it was found that pretreatment of the bath by vacuum can improve the coating quality. A new connector made of cross glass was designed and manufactured in the electroplating device. By using this updated device, a homogeneous Al coating ca.6μm in thickness was successfully electroplated on the internal surface of a Cu tube at 5 mA/cm2 for 1h.Finally, electroplating of Al on the internal surface of 316L stainless steel tube was carried out. The electroplated Al coating showed a high adhesion after an anodic electrolytic etching pretreatment of the stainless steel at 10mA/cm2 for 5min. The results obtained from researching the process parameters of Al electrodepositon shown that when the rotating speed of peristaltic pump was increased to 200r/min, the cell voltage can be remained stable. The maximum current density for electroplating depended on the diameter of Al wire used, which showed a linear relation. Moreover, the coating quality was obviously improved by removing the tube end face burrs and other measures. In the end, a high-adhesion homogeneous Al coating about 10μm thickness was successfully electroplated on the inter surface of a 316L stainless steel tube of 500 mm length and 11 mm internal diameter at plating parameter of 200r/min,3mA/cm2 and 3 hours. |
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