Cinnamic acid derivatives as inhibitors for dissolution of copper in phosphoric acid

Abstract

Although much work has been done on the rate of diffusion‐controlled corrosion under forced convection (moving solution), little has been done on the rate of diffusion‐controlled corrosion under natural convection which takes place in stagnant solutions. In diffusion‐controlled corrosion, the rate of corrosion is determined by the rate of transfer of the depolarizer or by the rate of removal of the corrosion products to or from the corroding surface respectively. In the case of stagnant solutions, transfer of the depolarizer to the corroding surface and removal of the corrosion products take place by diffusion and natural convection which arises from the density difference between the bulk solution and the interfacial solution, the interfacial solution being more dense than the bulk solution owing to the dissolution of the metal at the interface. This density difference result in a downward flow which enhances the rate of diffusion controlled corrosion. According to the hydrodynamic boundary layer theory the magnitude of natural convection depends on the physical properties of the solution us well as the geometry and orientation of the solid surface. Diffusion‐controlled metallic dissolution of vertical and horizontal surfaces has been studied earlier.