Don't let "dual protection" become "dual waste" - the process conflict and cost blind spot of steel structure galvanizing+painting combination

In the anti-corrosion design of steel structures, hot-dip galvanizing and on-site coating are often used in combination. The original intention was "dual protection", but if not handled properly, it can backfire.

The core of the problem lies in the compatibility of processes. The surface of the galvanized layer is smooth and chemically stable, making it difficult for ordinary coatings to achieve effective adhesion. Topcoats that have not been treated with specialized primer or interface pre-treatment typically develop bubbles and peeling within a few months. After the paint film is damaged, the originally sealed zinc layer is directly exposed, and factors such as local water accumulation and gap retention actually accelerate the corrosion process.

This creates a common dilemma: the cost of galvanizing has already been invested, and the cost of coating is added up, while the effective anti-corrosion life of the components has not increased but decreased.

From a cost perspective, the dual process not only brings about an increase in the cost per ton. Hidden expenses such as rework, project delays, and maintenance during the warranty period are often not fully estimated in the early stages of the project.

There is no universal solution for anti-corrosion of steel structures, and galvanizing and painting each have their own applicable boundaries. Applying the appropriate technology in the right place is a respect for project cost and a responsibility for the building's lifespan.