Metal Corrosion. Electroplating (Защита от металлов от коррозии. Гальванотехника). Я. Ившин

      4. Read and translate the text. Summarize it in Russian.

      Accelerated corrosion which can occur when dissimilar metals are in electrical contact in the presence of an electrolyte (i.e. conductive solution). An example of this corrosion phenomenon is increased rate of corrosion of steel in seawater when in contact with copper alloys. Galvanic attack can be uniform in nature or localized at the junction between the alloys depending on service conditions. Galvanic corrosion can be particularly severe under conditions where protective corrosion films do not form or where they are removed by conditions of erosion corrosion.

      Prevention or Remedial Action: selection of alloys which are similar in electrochemical behavior and/or alloy content; area ratio of more actively corroding material (anode) should be large relative to the more inert material(cathode); use coatings to limit cathode area; insulate dissimilar metals; use of effective inhibitor.

      (From www.galvanic-corrosion.com).

      5 . Read the text again. Decide whether the following statements are true or false.

      1. Accelerated corrosion phenomenon is decreased rate of corrosion of steel in seawater when in contact with copper alloys.

      2. Galvanic corrosion which can occur when dissimilar metals are in chemical contact in the presence of an electrolyte.

      3. Galvanic corrosion can be mainly partial under conditions where protective corrosion films form or where they are removed by conditions of erosion corrosion.

      6 . Work in pairs. Translate the following sentences from English into Russian.

      Many people utilized the standard galvanic series of materials in seawater to predict service performance relative to galvanic corrosion. In fact, this galvanic series is specific to only seawater at near ambient conditions. Other factors such as temperature and the presence of other chemical species can greatly affect the rank ordering of materials.

      Such differences in environmental conditions can reverse galvanic couples whereby the material expected to be the cathode may actually be the anode and experience severe corrosion.

      In making galvanic corrosion measurements, it is good practice to try to separate the effects if crevices between contacting materials and actual galvanic corrosion. This is the reason that in many tests, the actual electrical coupling of the two materials is performed in a region protected from the environment or externally from the environment. The external coupling is a good idea since it allows for measurement of the mixed potential of the couple and the galvanic corrosion current. While the potential serves as a measure of the thermodynamic driving force for galvanic corrosion, it is the galvanic corrosion current that indicates the acceleration of corrosion by the influence of the galvanic couple.