Corrosion Behavior Of Aluminized Layer Of Carbon Steel In Weak Acid Salt Solution

The corrosive environments of high temperature, high pressure and strong corrosiveand ultra-high flow rate of corrosive media, especially containing chlorides can cause steelequipment’s series of major issues and incidents. Protective coatings was used to improvethe corrosion resistance of iron-based alloys and particularly was an effective method forresistanting brine corrosion. Aluminized solid state technology can be much effective tostrengthen the surface, and the operation was very simple and convenient, therefore it hadbeen more widely used. This paper studied the corrosion behavior of Q235steel andaluminized steel in a variety of corrosive environments especially salt solution andexplored high corrosion resistance.which aluminized steel had in a variety of environments.We did solid aluminum test for Q235carbon steel, selected the best formulation andaluminized process. By XRD we analysed the aluminized layer’s phase composition, andobserved the aluminized layer’s microstructure. The results showed that formulations of20%aluminum powder+40%Al2O3+20%graphite+18%Fe2O3+2%NH4Cl was best,after980℃,6h aluminizing treatment, diffusion layer was dense, uniform, the bestsurface quality. Aluminized layer was mainly composed of FeAl, FeAl3metal, aluminizedlayer organization was a needle-like tissue.The Q235steel and aluminized steel immersioned in0.3mol/LNaCl differenttemperatures (20℃,40℃and60℃) and different NaCl concentrations under40℃(0.3mol/L,0.5mol/L and0.7mol/L) pH=6solution, did the indoor accelerated test andelectrochemical measurements, the sample was taken out for X-ray diffraction to analysisthe corrosion products. The results showed that: Q235steel and aluminized steel surfaceswere occurred uneven general corrosion and pitting, Q235steel’s corrosion products wereiron oxides, aluminized steel’s corrosion products was include aluminum compounds anddense not falling. The surface corrosion of Q235steel and aluminized steel was seriouswith increasing temperature, and was well with increasing salt concentration.In the samecorrosion environmengt, the surface of aluminized steel is to a lesser degree.Electrochemical experiments showed Q235steel and aluminized steel’s corrosioncurrent densities was accelerated with increasing temperature, Q235steel and aluminizedsteel’s resistance was decreased with increasing salt concentration; temperature at40℃with increasing salt concentration, the current densities was decreases and the resistancewas increased. Aluminized steel’s corrosion resistance was better than Q235steel.The Q235and aluminized steel was soaked at40℃0.3mol/LNaCl solution, pH=7aqueous and pH=10alkaline solution, did indoor accelerated test and electrochemicalmeasurements. The electrochemical experiments showed that in40℃, corrosion of NaClsolution of0.3mol/L was strongest, aqueous solution of pH=7was followed, alkalinesolution of pH=10was the lightest Aluminized steel’s corrosion resistance in weak acidsalt solution, neutral solution and alkaline solution were significantly better than the Q235steel, and the resulting of polarization curves and AC impedance spectroscopy wereconsistent.