Titanium alloy screws enjoy core advantages such as low density, high strength, excellent corrosion resistance, non-magnetism, and biocompatibility, and are widely used in high-end fields including aerospace, medical devices, marine engineering, high-end automotive and machinery, and precision equipment. However, the pure titanium and titanium alloy substrates themselves have shortcomings such as low surface hardness, insufficient wear resistance, prone to thread sticking, and monotonous appearance. Under high-frequency disassembly and assembly, high friction, and complex acid, alkali, and salt corrosion conditions, their service life and stability will be significantly limited.

Scientific and reasonable surface treatment is the core process to make up for the performance shortcomings of titanium alloy screws, enhance protective capabilities, optimize appearance texture, and adapt to special working conditions. The principles, performance, and costs of different surface treatment processes vary significantly. Precise selection can maximize the comprehensive value of titanium alloy fasteners. This article details the mainstream surface treatment processes, core advantages, applicable scenarios, and selection logic of titanium alloy screws in the industry.

I. Basic Pre-treatment Process: Establishing the Foundation for Surface Treatment
Pre-treatment is the initial process for all high-end surface treatments. Its core function is to remove oil stains, oxide scales, burrs, scratches, and surface defects generated during the screw processing, unify the surface condition of the substrate, enhance the adhesion of subsequent coatings or oxide films, and is the foundation for ensuring the quality of the finished product.
1. Sandblasting Treatment
Sandblasting is the most commonly used basic leveling process for titanium alloy screws. It uses high-pressure air to drive abrasive materials such as diamond sand and quartz sand to impact the surface of the workpiece, removing the surface oxide layer, machining burrs and sharp edges, and forming a uniform and fine matte finish.
This process can eliminate stress concentration on the screw surface, improve the roughness of the substrate surface, provide a high-quality attachment base for subsequent processes such as anodizing and painting. At the same time, it can slightly enhance the wear resistance of the screw surface, avoiding the problem of smooth titanium surfaces being prone to slipping. It is mainly applicable to aviation fasteners, outdoor equipment accessories, industrial equipment screws, etc., for products with basic requirements for uniform appearance and surface stability.
2. Polishing Treatment
It is divided into mechanical polishing and mirror polishing. Through grinding and fine polishing processes, it eliminates the knife marks and scratches on the screw surface, significantly improving the surface smoothness. It is divided into three grades: matte polishing, bright polishing, and mirror polishing.
The surface of the titanium alloy screws after polishing is smooth, fine, without flaws, with a high-grade texture, and can reduce surface pores, slightly enhancing the resistance to stains and corrosion. There is no coating residue, does not change the composition of the substrate, fully meeting medical and food-grade usage standards. It is mostly used for medical implant screws, high-end digital accessories, and decorative fasteners for precision instruments.

II. Enhanced Protective Core Technology: Functional Mainstream Processing Method
1. Anodizing (Coloring Oxidation)
Anodizing is the most widely used and cost-effective functional + decorative processing method for titanium alloy screws. It is suitable for all series of TA1, TA2 pure titanium and TC4 titanium alloys.
The principle of the process is to generate a 5-15 μm dense and uniform titanium dioxide oxide film on the surface of the screws through an electrolytic reaction. By adjusting the voltage (20-50V) and temperature parameters, various stable interference colors such as transparent, gun gray, black, gold, blue, and colorful can be produced. Under a temperature control of 300-400°C, a classic burn blue oxide film can be formed, with a film thickness of only 0.1-0.3 μm, which does not change the screw size or affect the mechanical properties of the base material.
Core advantages: Firstly, it significantly enhances the resistance to acid and alkali, as well as salt fog corrosion, suitable for humid and mild marine corrosion environments; Secondly, the film layer has extremely strong adhesion, is not prone to peeling, fading, or aging; Thirdly, it also has excellent decorative properties, with uniform and high-grade colors, without the cheap texture of electroplating; Fourthly, it has good insulation properties, avoiding metal electrochemical corrosion.
Application scenarios: It is suitable for high-end automotive and motorcycle modifications, outdoor new energy equipment, precision electronics, landscape equipment, etc., which balance corrosion resistance and appearance. It is also the mainstream processing method for high-end titanium screws in the civilian market.

2. PVD Vacuum Coating
PVD (Physical Vapor Deposition) coating is a high-end decorative and wear-resistant integrated processing technology. In a vacuum environment, metal ions are deposited on the surface of the screws to form hard coatings such as titanium nitride. The common colors include titanium gold, gun black, and multicolor, etc.
The hardness of the coating can reach 2000HV, and the wear resistance is more than three times higher than that of ordinary oxidation processes. It has excellent corrosion resistance, scratch resistance, and oxidation resistance, and the coating is fine and transparent, with uniform and high-grade color. There are no problems such as electroplating peeling or fading. It is environmentally friendly and pollution-free, and there is no heavy metal residue.
This coating combines top-level wear resistance and high-end decorative texture, and is suitable for scenarios such as high-end automotive and motorcycle modifications, luxury accessories, high-end digital precision fasteners, and aviation exterior decorative parts.
3. Low-Temperature Carbon Nitrogen Coating
This technology uses a low-temperature carbon-nitrogen co-coating process at 500-700℃. It forms a 5-50μm gradient coating layer on the surface of titanium alloy screws, with a surface hardness of 1100-1200HV. The thickness of the coating layer is 5-10 times that of ordinary ion implantation processes.
The greatest advantage of this process is that the low-temperature treatment does not damage the strength of the titanium alloy substrate, avoiding the problems of substrate softening and toughness reduction caused by high-temperature treatment. The coating layer is firmly bonded to the substrate, effectively improving the screw's resistance to wear, fatigue, and seizing, and is suitable for extreme industrial conditions such as heavy loads, high-frequency vibration, and high-strength friction. It is mostly used in heavy equipment and aviation load-bearing fasteners.

III. Selection Guide for Surface Treatment Processes of Titanium Alloy Screws
For titanium alloy screws under different working conditions and materials, precise matching of surface treatment processes is necessary, taking into account both performance requirements and cost control:
1. Ordinary civilian + appearance requirements: Priority should be given to anodizing and PVD coating, which also ensure corrosion resistance, decoration, and cost-effectiveness;
2. Medical + marine clean anti-corrosion requirements: Chemical passivation and mirror polishing should be given priority to ensure high cleanliness, high corrosion resistance, and biological safety;
3. High-frequency disassembly + anti-biting problem requirements: PTFE/ molybdenum disulfide lubrication coating must be selected to solve the core problem of thread locking;
4. Heavy load + high-temperature + extreme wear resistance requirements: Micro-arc oxidation and low-temperature carbon nitriding should be chosen to adapt to military and aerospace high-end working conditions;
5. Pure titanium light-load components: Sandblasting, passivation, and anodizing are the main processes; TC4 high-strength alloy heavy-load components: Micro-arc oxidation, carbon nitriding, and lubrication coating strengthening treatment should be given priority.
The core value of titanium alloy screws lies not only in the high strength and corrosion resistance of the base material, but also in the realization of performance improvement through refined and scenario-specific surface treatment processes. Optimized basic pre-treatment improves the surface condition, conventional oxidation and passivation processes lay a solid foundation for corrosion resistance, lubrication coating solves the practical pain points of threads, and high-end ceramic oxidation, PVD, and carbon nitriding processes are suitable for extreme high-end working conditions.
Reasonable surface treatment can completely solve the shortcomings of poor wear resistance, easy biting, monotonous appearance, and weak adaptability to working conditions of titanium alloy screws, significantly extending the service life of fasteners and improving the stability of equipment operation. This enables the high-end performance of titanium alloy fasteners to be maximally utilized in aerospace, medical, marine, and high-end manufacturing fields, and is a key link in improving the quality and efficiency of high-end industrial fasteners.