ELECTROCHEMICAL AND CORROSION-MECHANICAL PROPERTIES OF PIPE STEEL OF DIFFERENT STRENGTH LEVEL IN MODEL SOIL ELECTROLYTE

Abstract

Determine the influence of the strength category of the pipe steel on the electrochemical and corrosion-mechanical properties under the conditions of the combined effect of constant deformation
and protective potential in a weakly alkaline environment. The  standard  methods  were  used:  the  massometry  method,  the  potentiometry,  the polarization  curves,  the  method  for  investigating  the  resistance  to  corrosion  cracking  under  constant deformation at the cathode potential.  The  rate-control  reaction  of  anodic  dissolution  of  both  steel  in  model  soil  electrolyte  is oxygen diffusion, on what the values of Tafel slopes point out. It was noted that hydrogen reducing on X80 steel  carry  on  easier  than  on  X70  steel.  Under  conditions  of  constant  deformation  for  X70  steel,  the undersurface orrosion is more typical for X80 steel –  intergranular cossorion. Originality According to the results of comparative tests it was established that the rate of anodic dissolution of X80 and X70 steel is controlled by oxygen diffusion in a slightly alkaline solution. It was noted that hydrogen reducing carry on easier on X80 steel than on X70 steel. Practical  value.  Under  conditions  of  constant  deformation,  for  steel  X70  subsurface  corrosion  is more  characteristic,  and  for  X80  steel  –intergranular  corrosion  is  more  typical.  The  propagation  of intergranular corrosion in steel is more dangerous during in operation, as it may cause to cracking  under strain stress.