Golden Hard Anodizing

(Japanese patent)

G.H.A.® is the most recent and innovative technology applicable to the surfaces of all the aluminium alloys (light alloys).
G.H.A.® is a special anodic oxidation treatment with adjustable thickness from 1 to 100µm and subsequent sealing of the micro porosities by silver ions (Ag+).
The high hardness of anodic oxide (HV 500-550), together with the extraordinary properties of silver ions (see table 1), give to the treated surface biotechnological characteristics of the utmost interest for applications (see table 2) ranging from the pharmaceutical and alimentary field to the technical and scientific field:

- components of industrial machines for reducing wear and corrosion - automotive components - components for office machines - components for kitchens and household appliances - components for residences and relevant accessories - components for electronics-semiconductors - radiators, heat exchangers, solar panels - clothing, electric blankets, carpets - filters for air-conditioners

Fig. “A” example of G.H.A.® oxidation with 30µm thickness

Table 1

Silver ions Ag+ properties
High antibacteric and antimould capacity (bacteriostatic) Low coefficient of friction, self-lubrication and resistance to wear Resistance to corrosion High thermal conductivity and high thermodynamic yield Electric conductivity and antistatic characteristics Capacity to absorb heat and to return it by infrared emissions

Table 2

Biotechnological characteristics
Material	Hardness HV	Melting Temperature °C	Coefficient of friction	Bacteriostatic capacity	Corrosion resistance SST	Wear resistance
Aluminium alloy	70÷100	680°C	0,44	none	100 hours	102 hours
Aluminium oxide G.H.A.® treated	500÷550	2100°C	0,025	very high	10.000 hours	105 hours
Hard anodizing	500÷550	2100°C	0,15	none	200÷500 hours	103 hours

Please notice that the thickness of the treatment, ranging from 1 to 100µm is not removable, because the anodic oxides are directly developed on the surface of the workpiece, that acts as the anode, producing an oxidised layer that 50% diffuses inside the workpiece and 50% grows on the surface (see fig. A).
The G.H.A.® treatment is also very interesting from an economic point of view, because it uses the silver, an expensive metal, in its atomic condition that is very small and homogeneously distributable. The silver ion is very reactive and it gives the outstanding properties listed in the table.