What Are the Anti-Rust Measures for Wedge Anchor Bolts When Installing GRC Components? Qinglong GRC Anchoring System Anti-Rust Process Explained

As a common fastener for the post-installed fixing of GRC components, the rust resistance of nail-in anchors (i.e., hammer-set anchors/expansion bolts) is directly related to the long-term safety of connection joints. In humid environments, especially coastal ones, screw corrosion can lead to reduced load-bearing capacity or even failure. For different application scenarios, Qinglong GRC has established full-process anti-rust control standards covering screw material selection, surface treatment, installation techniques, and post-installation sealing.

In a post-installation project for GRC decorative moldings at a seaside plaza in Xiamen, the original design specified ordinary galvanized nail-in anchors. After evaluation, the Qinglong technical team judged the risk to be high and changed them to top-grade rust-resistant screws made of A4-80 grade (316) stainless steel. Installation strictly followed the procedure of “hole cleaning, drying, adhesive injection, and screwing in”: the hole was first thoroughly cleaned with a rubber blower, an appropriate amount of epoxy resin anchor adhesive was injected, and the stainless steel nail-in anchor was then hammered into place. This not only encapsulated the screw shank with the adhesive's corrosion-resistant colloid, but also significantly improved its pull-out resistance. The project has withstood multiple typhoon seasons without any corrosion at the anchor points.

Optimal Selection of Screw Base Materials and Surface Treatment

This is the first line of defense against rust. In severe environments (C4-C5), nail-in anchors made of A4 (316) stainless steel must be selected, as their high molybdenum content resists chloride ion corrosion. In general humid environments (C3), A2 (304) stainless steel or carbon steel screws with Dacromet (zinc-aluminum coating) treatment may be used. Ordinary galvanized screws (even hot-dip galvanized) will still rust in long-term humid environments and are not recommended for exposed or critical connections of important GRC components.

Dual “Physical + Chemical” Anti-Rust Protection in Installation Techniques

Rust resistance of the screw alone is not enough; it must be combined with installation techniques. Chemical anchoring is the best option: inject epoxy resin or vinyl ester chemical anchor adhesive into the drilled hole, then insert the screw. Once cured, the adhesive bonds the screw and the concrete hole wall into one unit and forms a dense protective layer that completely blocks moisture vapor and oxygen, providing excellent rust protection while greatly increasing load-bearing capacity. For dry installation, the drilled hole must be kept dry and dust-free, and after the screw is inserted, a small amount of sealing compound should be applied under the screw head and washer.

Sealing and Inspection After Installation

Once the screws are in place, the exposed screw heads, washers, and surrounding areas are the weak points for rust protection. Weather-resistant sealant or anti-corrosion putty should be applied to cover and seal the screw heads, forming a flexible protective layer. For screws installed in rows, decorative cover caps may be considered. Establish a regular inspection plan to spot-check screws at representative locations every 2-3 years for signs of rust and seal integrity.

Design Optimization to Reduce Corrosion Risk

Avoid risks at the design source. Whenever possible, avoid placing post-installed anchors on horizontal surfaces or recesses prone to water accumulation. Embedment depth should meet code requirements to ensure sufficient bond strength and protective cover. Where possible, give priority to embedded inserts for connections, as their anti-rust treatment can be more strictly controlled in the factory, offering higher reliability than post-installed anchors.

Though small, nail-in anchors are vital to the installation safety of GRC components. Qinglong GRC adheres to the principle of “optimal material selection, standardized techniques, and meticulous sealing.” Its anchor system anti-rust processes have been developed into standardized operating procedures, effectively safeguarding the long-term safety of GRC components in various projects, especially in severe environments.