ANODIC PROTECTION. Feasibility of anodic protection is firstly demonstrated and tested by Edeleanu in 1954. Corrosion control of metal structure by impressed anodic current. Interface potential of the structure is increased into passive corrosion domain.
Feasibility of anodic protection is firstly demonstrated and tested by Edeleanu in 1954
Interface potential of the structure is increased into passive corrosion domain.
Protective film is formed on the surface of metal structure which decrease the corrosion rate down to its passive current.
Can be applied for active-passive metals/alloys only.
Anodic protection of 304SS exposed to an aerated H2SO4 at 300C at 0.500 vs. SCE
Titanium and chromium can be passivated very easily and their passivation process will occur more often than not, spontaneously, even in the absence of oxidizing agent.
(can be obtained from anodic polarization measurement)
Optimum potential for anodic protection is midway in the passive region
In which EFO : Flade potential at pH = 0
n : a constant (between 1 and 2) depends of metal composition and environment conditions
Parameters that should be considered for anodic protection design (Flade potential is not included in the figure)
Influences of temperature and chloride concentration on anodic polarization curve of stainless steels
Anodic polarization curves of a mild steel in 10% sulfuric acid at 22 and 600C
Schematic figure of potential range for anodic protection of a stainless steel which is susceptible to pitting corrosion in an environment containing aggressive ions
Schematic figure of anodic protection system for protecting inner surface of storage tank
Platinum clad brass can be used for anodic protection cathodes because this cathode has low overpotential and its degradation rate is very low, however it is very expensive.
Effect of chromium content on critical current density and Flade potential of iron exposed in 10% sulfuric acid.
Effects of nickel and chromium contents on critical current density passivation potential in 1N and 10 N H2SO4 containing 0.5 N K2SO4
Requirement of critical protection current densities for several austenitic stainless steels (18-20 Cr , 8-12 Ni) exposed in different electrolytes
Protection current density :current density required to maintain passivity
Effect of sulfuric acid concentration at 240C on the corrosion rate and critical current density of stainless steel
Effect of stirring of electrolyte on the corrosion rate and requirement of current density to maintain passivity on a stainless steel at 270C
A cylindrical tank of 304 stainless steel for storing deaerated sulfuric acid (pH=0) is found to corrode rapidly. To provide anodic protection, a galvanic cathode of platinum will be installed. The tank has a diameter of 5 m and the depth of acid is 5 m.