Study On The Corrosion Behavior Of Connection System Of Stainless Steel To SMA And The Elimination Systerm Of Water Or Sand In Crude Oil

Fe-based shape memory alloy pipe was widely used to the construction structures in resent years with its unique advantage. Shape memory alloy connection is a new kind of connection method for pipeline. When use those method,the choice of stainless steel tube is a very important. The pitting potential and the galvanic corrosion should be considered. The fill stuff of Tachoing complex connection was study in this paper. It is founded that the best ratio of phosphoric acid solution and CuO is 1:3, the value of connection stress is about 6.3e~6N/m~2. The gap of stainless pipe and Shape memory pipe is a important factor affect the strength of connections, to a certain extent , the greater bonding strength is increased as the gap decreased. The pitting potential of different stainless steel with polarization curves with method was studied. It was found that pitting potential of different stainless steel varies widely. The pitting potential of stainless steel for surface with veins(FW) is better than for the surface is like mirror(JM). Cr element has a great influence on the pitting potential. Pitting potential of 445FW stainless steel which has more Cr is greater than 441FW stainless steel. In addition, the grain size of the crystals is very important to the corrosion performance. Because the size of 304FW grain is bigger than 304JM, the pitting potential of 304FW stainless steel is far greater than 304JM. The different surface treatment method of the stainless steel is also important for the corrosion performance. In this paper, the galvanic current between the heated SMA and three stainless steel were measured through the electrochemical system. It is manifest that 304 stainless steel is more suitable to connections to SMA pipe.In the offshore oil industry, acetate and methanol mixed solution was used for the removing of sand and sea water which ensuring not freezing in low-temperature environment. It is found that the proportion of acetic acid and water for 75%: 25% of the mixture in an environment of -30oC in 10 days has not frozen. The corrosion performance of carbon steel and stainless steel in the above system were studied. Corrosion rate of those two kind of material in acetic acid(75%) and methanol (25%) are wose than in acetic acid (75%)and water(25%) system.. So it is feasible that water can replace methanol in the removing of sand and sea water system. At the same time, a inorganic inhibitor (Copper sulfate) and an organic corrosion inhibitors (Urotropine) were selected, it is found that for carbon steel the former is better than inhibitor CRW85582 and CRW82328,and the latter is also better than inhibitor CRW82328(used in project)for carbon steel and stainless steel.