In the automotive painting pretreatment process, one-step phosphating method is suitable for bodies with an aluminum content of ≤40%, while two-step phosphating (phosphating + passivation) can handle high-aluminum or all-aluminum bodies. This paper compares their process characteristics, consumable consumption, and body appearance quality. Case analysis reveals that when the aluminum content is low (below 30% in this case), the two-step method consumes approximately 20% more materials per vehicle than the one-step method. Furthermore, the two-step process is prone to causing streaks and pit defects on the surface of aluminum outer panels after electrophoretic painting. These streak defects can be mitigated by optimizing phosphating parameters and spray processes, while pitting defects can be reduced by adjusting the aluminum sheet's Electro Discharge Texture(EDT) process. The research demonstrates that for production lines with low aluminum content, the one-step phosphating method holds significant advantages in both economy and final quality.

Pretreatment  /  Phosphating  /  Passivation  /  Phosphating Streaks  /  EDT Scales