Bolt ball space frames, as an efficient spatial structural system, are composed of interconnected members in a three-dimensional grid and are widely used in large public and industrial buildings such as sports arenas, convention centres, coal storage sheds, warehouses, and transport hubs.
However, these structures are often exposed to harsh outdoor environments, facing corrosion risks that are a primary factor reducing load-bearing capacity and raising maintenance costs. Inadequate maintenance causes rusting, significantly affecting structural safety and performance, so targeted bolt ball space frame anti-corrosion work is vital for long-term structural stability.
Therefore, implementing a comprehensive corrosion protection strategy throughout the entire life cycle is critical to ensuring structural integrity, operational reliability, and extended service life. This paper examines the primary corrosion mechanisms affecting bolt ball space frames and systematically outlines proven corrosion protection technologies and practical protection strategies suitable for various operating environments.
Key Principles of Bolt Ball Space Frame Anti-Corrosion
Atmospheric Corrosion in Outdoor Environments
For bolt ball space frame anti-corrosion work, atmospheric corrosion is the most widespread outdoor risk. When steel components are exposed to moisture, oxygen, and pollutants in the air, oxidation reactions gradually occur and cause rust formation.
In industrial environments, corrosive gases such as sulfur dioxide and nitrogen oxides may combine with moisture to create acidic conditions, accelerating steel corrosion. Coastal areas present additional challenges, as high humidity and salt spray can significantly increase corrosion rates. Without proper protection and maintenance, surface coatings may gradually deteriorate, affecting the structural safety and service life of the space frame system.
Galvanic Corrosion at Bolt Ball Connections
Galvanic corrosion is another important factor that should be considered in bolt ball space frame systems. Since these structures consist of multiple components, including bolt balls, high-strength bolts, sleeves, and connecting parts, different metals may come into contact during assembly.
When these dissimilar metals are exposed to moisture, an electrochemical reaction may occur, causing accelerated corrosion at connection areas. Because corrosion often develops inside joints or hidden contact surfaces, it can be difficult to detect during routine inspections. Therefore, selecting compatible materials and applying effective protective measures are essential for preventing connection deterioration.
Stress Corrosion and Structural Safety Risks
Stress corrosion is closely associated with the load-bearing condition of bolt ball space frames. During long-term operation, structural components are continuously subjected to various stresses from self-weight, external loads, wind forces, and environmental changes.
In areas with stress concentration, such as joints and connection points, corrosion can combine with mechanical stress to create micro-cracks and gradually weaken the structure. If these issues are not identified and treated in time, they may reduce load-bearing capacity and increase the risk of structural failure.
Corrosion Risks in Different Application Environments
The corrosion risk of bolt ball space frames varies depending on the installation environment. Therefore, evaluating environmental conditions is a critical step in developing an effective anti-corrosion strategy.
For example:
- Industrial buildings, such as coal storage sheds and warehouses, may face corrosion caused by dust, chemicals, and industrial gases.
- Coastal sports venues and public buildings require enhanced protection against humidity and salt spray.
- Chemical plants need special consideration for exposure to acidic or alkaline substances.
To achieve long-term durability, bolt ball space frame components should receive customized corrosion protection treatments according to the specific environmental corrosion level. Proper material selection, surface protection, and regular maintenance can significantly extend the service life of the structure.
Key Anti-Corrosion Measures at the Design Stage
Anti-corrosion design is the starting point of full-lifecycle protection. Scientific and rational upfront planning can substantially reduce later maintenance costs. The key measures at this stage include:
- Appropriate design allowances
Standardized bolt ball space frame anti-corrosion design reserves thickness allowance for long service life.These reserved margins are the first line of defence against corrosion. Based on the corrosion rate of the structure’s environment, adequate cross-sectional allowances should be reserved for critical load-bearing members to ensure that, even after a certain degree of corrosion over the intended service life, the structural capacity remains safe.
- Joint detailing optimisation
Joints of bolt ball space frames should be designed to avoid water ponding, crevices, and other areas prone to moisture and corrosive media accumulation. Unused bolt holes on the balls should be sealed with putty to prevent corrosive gas ingress, and water-stop grooves can be provided at installation end faces to block moisture penetration paths.
- Material selection
This directly determines the inherent corrosion resistance of the structure. In moderately corrosive environments, weathering steel can be used, as its dense rust layer effectively impedes further corrosion. In highly corrosive environments, galvanised steel or composite stainless steel materials are preferable. For bolt ball space frames, composite or pure stainless steel can be adopted to enhance corrosion resistance.
- Anti-corrosion coating system design
A complete coating system typically consists of a primer, intermediate coat, and topcoat selected as a compatible set. Epoxy zinc-rich primer is recommended for the primer layer, utilising the cathodic protection of zinc to provide underlying defence; the intermediate coat acts as a barrier; the topcoat offers weather resistance and aesthetics. The selection of the coating system should be determined comprehensively based on the corrosion environment category, design service life, and maintenance conditions.
Anti-Corrosion Control During the Fabrication Stage
Quality control during fabrication directly determines coating system performance and is critical for effective anti-corrosion. The main fabrication controls are:
Surface preparation: Fundamental to coating quality, members and balls should be descaled by shot or grit blasting to Sa 2.5 — meaning free of visible oil, grease, dirt, mill scale, rust, and coatings, with only slight stains in spots or stripes permitted. This ensures optimal adhesion.
Coating application: Controls film thickness, adhesion, and uniformity. Each coat—primer, intermediate, topcoat—must follow prescribed procedures at 5–38°C and ≤85% humidity. Thickness must meet design, with adhesion tests verifying quality.
Hot-dip galvanising: Hot-dip galvanizing is the most reliable bolt ball space frame anti-corrosion treatment for coastal projects. An important long-life method, it involves immersing pre-treated workpieces in molten zinc (~450°C) to form a zinc-iron alloy and pure zinc layer, isolating air/moisture and providing sacrificial protection. In corrosive environments, it is commonly used for bolt ball space frames, with thickness not less than 80 μm.
Bolts and sleeves: Vulnerable connections need reinforcement. High-strength bolts should be galvanised; set screws preferably stainless. During galvanising, protect threads, nut inner mouths, contact areas of cone heads/sealing plates, and bolt ball threaded holes. For complex parts, Dacromet coatings improve salt-spray resistance.
Conclusion
Bolt ball space frame anti-corrosion protection requires a comprehensive approach covering design, fabrication, and operation.Proper material selection, optimized joint design, high-quality coatings, hot-dip galvanizing, and regular maintenance all work together to improve corrosion resistance, extend service life, and reduce long-term maintenance costs.
Different environments require different protection strategies. Coal sheds and warehouses need resistance against dust and corrosive gases, coastal structures require enhanced salt-spray protection, and chemical plants need solutions for acidic and alkaline conditions. By implementing targeted anti-corrosion measures, bolt ball space frames can maintain reliable performance in various applications.
Yunjoin has extensive experience in bolt ball space frame anti-corrosion. The company produces 50,000 tonnes annually, with eight advanced automated production lines. All accessories, including cone heads and bolt balls, are designed and manufactured in-house. Its R&D team is proficient in CAD, PKPM, SAP2000, Tekla, and ANSYS, providing customised full-process solutions from design to installation for coal sheds, arenas, hangars, and more, tailored to specific corrosion grades and project requirements.
