What Effects Can Surface Acid Pickling Achieve on UHPC Panels? The Process Secrets of Controlled Corrosion and Activated Texture

Acid pickling treatment of UHPC panel surfaces is an advanced surface treatment process that uses controlled chemical corrosion to highlight the aggregate texture, create rich visual layers, and enhance surface adhesion. Through precise control of the acid type, concentration, temperature, and action time, Qinglong Group can achieve a series of artistic effects, from the fine texture of "slightly exposed aggregate" to the rugged texture of "strong erosion," while significantly improving the adhesion of subsequent coating systems.

The core principle of acid pickling is to use an acid solution (usually a diluted solution of hydrochloric acid, fluorosilicic acid, or phosphoric acid) to selectively corrode the cement paste on the UHPC surface, allowing the harder aggregates (such as quartz sand) and steel fibers to be exposed. The treated surface presents a natural, granite-like speckled or uniform rough texture. The specific effect achieved depends on three levels: first, the visual level—the color and distribution of the exposed aggregates form unique decorative patterns, breaking the original uniform gray tone of UHPC; second, the tactile level—the surface becomes rough with subtle undulations, enhancing the material's tactile appeal and slip resistance; third, the physicochemical level—the corroded surface develops more micropores and a larger specific surface area, providing an excellent mechanical interlocking foundation for subsequent coating, with pull-off adhesion typically improved by more than 50%.

Take as an example the acid-pickled UHPC panels our company supplied for the exterior wall project of a modern art museum: we used a hydrochloric acid solution at a concentration of 5%-10%, spray-treated at room temperature for 3-5 minutes. Through real-time monitoring, when the surface cement paste had been moderately etched to a depth of approximately 0.5-1mm and the uniformly distributed light gray quartz sand particles were clearly exposed, we immediately rinsed thoroughly with a high-pressure water gun to neutralize and remove residual acid. The final result: the panel surface presented a uniform light gray sesame-dot effect, with a texture that is fine yet rugged, producing rich light and shadow variations under sunlight. More importantly, after this treatment, when the panel surface was sprayed with fluorocarbon paint, the coating adhesion tested by the cross-cut method reached Class 0 (no peeling), far exceeding that of untreated surfaces.

The key to the acid pickling process lies in "control." The acid concentration, temperature, and action time must be determined through preliminary tests based on the specific mix proportion of the UHPC (especially the cement type and aggregate hardness). Over-pickling can cause aggregates to loosen or even fall off, and steel fibers to be excessively exposed and rust; insufficient treatment, on the other hand, produces an unnoticeable effect. Qinglong Group has a well-equipped pretreatment laboratory that can customize the most suitable pickling formula and process parameters for each project, thereby stably reproducing the unique texture desired by designers.