Electrochemical protection of ammonia liquor storage tanks
Cathodic protection was installed on the storage vessels. Four anodes were installed on each vertical tank and two on each horizontal tank. The anodes were tubes of grade 1Kh18N10T stainless steel with flanges screwed onto one end. The flange is held between two insulating textolite spacers and the branch flange, and is completely insulated from the storage tank. The end of the anode is 15 cm from the tank bottom and it has a rod for connecting it to a potential controller. The total surface of the anodes in a tank of 400 m/sup 3/ capacity is 2.84 m/sup 2/. An intermittent potential controllers is used in the system. The immersion reference electrode phi/sub 1/ is made of type ATM-1 graphite, the two electrodes are passed through special branches located opposite each other and adjacent to the tank wall. The reference electrode had an output terminal for connecting to the potential controller. The graphite electrode poential is stable in ammonia liquor and is more negative than that of the silver chloride electrode. The electrical circuit for the cathodic protection is shown. The storage tank filled with ammonia liquor is passivated by means of welding equipment. The equilibrium potentials of the storage tanks relative to the graphite electrode potentials are in the active solution range of grade St 3 steel. The initial passivation current of 40 to 60 A was maintained for 0.5 to 1.0 h and the current was then reduced to 10 A. During this time the potential changed gradually to /sub phi prot/. It was then switched over to automatic control by means of an intermittent potential regulator at the established /sub phi prot/. The mean annual corrosion rate determined by control samples under protection confirms that cathodic protection reduces the corrosion rate for carbon steel in ammonia liquor by a factor of three or more (in certain cases up to 40).
- OSTI ID:
- 5570763
- Journal Information:
- Coke Chem. USSR (Engl. Transl.); (United States), Vol. 2; Other Information: Translated from Koks Khim.; No. 2, 43-45(1980)
- Country of Publication:
- United States
- Language:
- English
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