Hard Anodizing

OX-W is a special aluminium hard anodizing treatment in compliance with MIL-A-8625 Type III, ISO 10074, and UNI 7796 standards.

Compared to conventional hard anodizing treatments, the OX-W treatment was developed to increase the characteristics of hard anodizing and obtain a more compact and uniform aluminium oxide film, with lower surface roughness and higher corrosion resistance.

It allows the achievement of high salt spray corrosion resistance with reduced anodizing thicknesses and on hard-to-process alloys such as series 2000 alloys and high-silicon content casting alloys.

It is also employed to treat parts for gas distribution and control (natural gas, hydrogen, and oxygen), in which properties of low surface roughness and high scratch and wear resistance are required.

Packaging machine parts, OX-W anodizing


The compact OX-W film protects the substrate material from corrosion, exceeding 336 hours of salt spray exposure, with no trace of corrosion.


The hardness and compactness of the aluminium oxide layer allows the achievement of high abrasive and adhesive wear resistance, comparable to that of hard chrome.


The OX-W treatment creates a more compact and uniform layer of aluminium oxide with lower surface roughness than that of conventional hard anodizing treatments.


OX-W treatment has a light grey colour with shades that depend on the treated aluminium alloy.


To reduce the friction coefficient and impart non-stick properties, the OX-W treatment can be impregnated with PTFE nanoparticles.


Composition and applicable standards

The OX-W treatment transforms the aluminium substrate into a compact layer of aluminium oxide. The coating composition is thus strongly dependent on the starting alloy.
20÷40%50÷70%3÷5%Depending on the alloy
Technical standards
ISO 10074
UNI 7796
MIL-A-8625 | Type III
RoHS compliance
RoHS compliant. No restricted substances present in amounts greater than the maximum tolerated concentrations.
REACH compliance
REACH compliant. No SVHCs present in amounts higher than 0.1% by weight.

Anodizable alloys

Wrought alloysCharacteristics
Series 2000Hardness★★★☆☆
Wear resistance★★★☆☆
Corrosion resistance★★★☆☆
Maximum thickness★★★☆☆
Series 5000 (with >2% Mg) and 7000Hardness★★★★☆
Wear resistance★★★★☆
Corrosion resistance★★★★☆
Maximum thickness★★★★★
Series 6000 (except 6082, 6061)Hardness★★★★★
Wear resistance★★★★★
Corrosion resistance★★★★★
Maximum thickness★★★★★
6082, 6061Hardness★★★★★
Wear resistance★★★★★
Corrosion resistance★★★★★
Maximum thickness★★★★☆
Casting alloysCharacteristics
Alloys with Si>8% or Cu>2%Hardness★☆☆☆☆
Wear resistance★☆☆☆☆
Corrosion resistance★☆☆☆☆
Maximum thickness★☆☆☆☆
Die castings with Si<8% or Cu< 2%Hardness★★☆☆☆
Wear resistance★★☆☆☆
Corrosion resistance★★☆☆☆
Maximum thickness★☆☆☆☆
Other alloysHardness★★☆☆☆
Wear resistance★★☆☆☆
Corrosion resistance★★★☆☆
Maximum thickness★★★☆☆

Treatment thickness and aesthetic appearance

Coating thickness
Standard thicknessTolerance
50% of the treatment thickness is due to external film growth and 50% is due to film growth in the surface of the aluminium part. The radial dimensional increase can thus be calculated as half the treatment thickness.
Adjustment of dimensional values following hard anodizing
Uniform thickness over the entire external surface. Reduced thickness in holes.
Aesthetic appearance
Slightly matt appearance with light grey colour. The colour depends on the base alloy and the treatment thickness. Reproduces the morphology of the machined part.

Tribological properties

The OX-W treatment features high film hardness. The value varies in accordance with the treated alloy.
Hardness valueAlloy
Series 2000
Series 5000 (with >2% Mg) and 7000
Other wrought alloys
Wear resistance
OX-W offers very high abrasive and adhesive wear resistance. The value varies in accordance with the treated alloy.
Wear value, TWI-CS17Alloy
The lower the number, the higher the performance – MIL-A-8625F and ISO 10074 C.3 – Taber Abraser wear test – CS 17 abrasive wheels – 1 kg load
< 35 mg / 10 000 cycles
Series 2000
< 25 mg / 10 000 cycles
Series 5000 (with >2% Mg) and 7000
< 15 mg / 10 000 cycles
Other wrought alloys
Friction coefficient
The OX-W-PTFE variant features an impregnation treatment of the anodized film with PTFE nanoparticles.
The impregnation process makes it possible to obtain a non-stick, self-lubricating surface with a low friction coefficient.

Chemical properties

Corrosion resistance
The OX-W treatment makes it possible to achieve high corrosion and oxidation resistance. The treated surface passes 336 hours of salt spray exposure, with no trace of corrosion.
Corrosion resistance valueSubstrate material
NSS in compliance with ISO 9227 and ISO 10074
≥336 hours without corrosion6000 alloy
Chemical resistance
Chemical compatibility values. The actual environmental resistance must anyway be tested in the field.
Hydrocarbons (e.g. petrol, diesel, mineral oil, toluene)
Alcohol, ketones (e.g. ethanol, methanol, acetone)
Neutral saline solutions (e.g. sodium chloride, magnesium chloride, seawater)
Dilute reducing acids (e.g. citric acid, oxalic acid)
Acid oxidizing agents (e.g. nitric acid)
Concentrated acids (e.g. sulphuric acid, hydrochloric acid)
Dilute bases (e.g. dilute sodium hydroxide)
Base oxidizing agents (e.g. sodium hypochlorite)
Concentrated bases (e.g. concentrated sodium hydroxide)