The scratch resistance of glass door hardware is mainly determined by the surface treatment process. Among them, the hardness of the physical vapor deposition (PVD) coating can reach 2,000-3,000 HV (Vickers hardness), far exceeding the 300-500 HV of traditional electroplating, and the scratch resistance performance is improved by 5-8 times. For example, the PVD titanium coating of Hafele in Germany, through multi-layer superposition technology (thickness 1.5-3μm), can withstand 10,000 cycles of wear (load 1kg, CS-10 grinding wheel) in the Taber Abraser test. The mass loss is only 0.8mg (15mg for the common electroplating layer). In 2023, the Atlantis Hotel in Dubai adopted this type of coating. Within five years, the complaint rate of door handle scratches dropped from 12% to 0.3%, and maintenance costs were saved by 46,000 US dollars.
Anodizing is another cost-effective option. The hardness of hard anodizing (Type III) reaches 600-800 HV, the thickness of the oxide film is 50-100μm, and the salt spray corrosion resistance life exceeds 3,000 hours (ASTM B117 standard). The aluminum alloy handles of the American brand Emtek, after hard oxidation, achieve a scratch resistance level of 8 in the Mohs hardness test (while ordinary oxidation only has a level of 5). They are suitable for high-frequency usage scenarios such as hospitals (with an average of 200 switches per day). After five years, the surface wear rate is only 5% (while the wear rate of ordinary coatings is 40%).
Nano-ceramic coatings (such as Cerakote) combine chemical stability with mechanical strength. Its hardness is 9H (pencil hardness test), the wear resistance index is 4,500 revolutions (ASTM D4060 standard, load 1kg), and the impact strength is 50 J/cm² (traditional baking varnish is only 20 J/cm²). After the sliding door accessories of the British brand UltraLox adopted this technology, under the extreme passenger flow pressure at London Heathrow Airport (with an average daily usage of 3,000 times), there were no visible scratches within two years, and the maintenance cycle was extended to 10 years (ordinary coatings need to be refurbished every 3 years).
Cost and performance need to be balanced. The investment in PVD coating equipment can be as high as 500,000 to 1,000,000 US dollars. The cost per piece is 30-50% higher than that of electroplating, but the life cycle cost is reduced by 60% (calculated over 10 years). For instance, when a commercial complex purchases PVD-coated door locks (with a unit price of 120 US dollars), compared with electroplated locks (with a unit price of 80 US dollars), the total cost over 10 years is saved by 45 US dollars per piece (the maintenance cost is reduced from 120 to 30 US dollars). While electrostatic powder coating (with a thickness of 60-120μm) has a low cost (0.5-1 US dollars per piece), its scratch resistance is only 2 hours and it is suitable for low-flow areas (such as residential bathrooms).
Compliance and environmental protection indicators influence the choice. The EU RoHS certification requires that the hexavalent chromium content of the glass door hardware coating be ≤ 0.1%, while the PVD process is completely chromium-free (Cr⁶⁺ detection value 0%). In 2022, a school in California was fined $87,000 for using chromium-plated accessories. After switching to PVD, the compliance risk was reduced to zero. In addition, the volatile organic compound (VOC) emissions of the nano-coating are ≤ 50g/L (the national standard limit is 250g/L), meeting the requirements of LEED green building certification.
Verify performance in extreme environments Hotels within the Norwegian Arctic Circle use glass door hardware with DLC (diamond-like carbon) coating (with a hardness of 5,000 HV). Under a temperature difference ranging from -40℃ to 80℃, the adhesion of the coating still reaches ISO 2409 Class 0 (without peeling). Under the same conditions, 30% of the common coatings cracked. The initial cost of this type of coating is twice that of PVD (about $200 per piece), but it extends the maintenance interval from 2 years to 15 years, making it suitable for harsh scenarios such as polar regions and chemical industries.