Within how many days of being cleaned should primer be applied to an existing steel structure being painted?

The appropriate timeframe for applying primer to an existing steel structure after it has been cleaned is typically within three days. This time limit is essential to ensure that the underlying surface is adequately prepared for coating. After cleaning, the surface should remain free of contaminants such as rust, dirt, oil, or moisture, which can compromise the adhesion and overall effectiveness of the primer.

If primer is not applied within this critical window, the newly cleaned surface may develop contaminants or oxidization due to exposure to air and moisture, which could negatively affect the performance of the primer and subsequent paint layers. Thus, applying the primer promptly within three days helps maintain the integrity of the preparation process and ensures optimal adhesion of the coating system, ultimately leading to a more durable finish.

Other time frames, such as five, seven, or ten days, would typically be considered too long and could introduce risks such as surface contamination, and would not align with best practices in surface preparation in the painting of steel structures.