Hard Anodizing

OX-HS is a hard anodizing treatment of aluminium in sulphuric acid in conformity with MIL-A-8625 Type III, ISO 10074 and UNI 7796 standards.

High corrosion resistance

The compact layer of OX-HS protects the base material from corrosion and brilliantly withstands 336 hours of exposure to salt mist without any corrosive attack.

High wear resistance and hardness

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

High thickness 40-60µm

The high treatment thickness, typically 40-60µm, permits obtaining high duration in aggressive environments.

OX-HC black colour variant

The OX-HS treatment can be pigmented deep black, thereby making the colour uniform on all aluminium alloys.

Low friction OX-W-PTFE variant

To lower the friction coefficient and provide anti-adhesion properties, the OX-HS treatment can be impregnated with PTFE nanoparticles.


The OX-HS treatment transforms base aluminium into a compact layer of aluminium oxide. The composition largely depends on the initial alloy.
Al O S Impurities
20÷40% 50÷70% 3÷5% Depending on alloy
Product technical standards
ISO 10074
UNI 7796
MIL-A-8625 | Type III
RoHS Conformity
RoHS conform. No restricted-use substances beyond maximum tolerated concentrations.
REACh Conformity
REACh conform. No SVHC in quantities greater than 0.1% by weight.
Anodizable alloys
Wrought alloys Hardness Wear resistance Corrosion resistance Max thickness
Series 2000 ★★★☆☆ ★★★☆☆ ★★★☆☆ ★★★☆☆
Series 5000 (with >2% Mg) and 7000 ★★★★☆ ★★★★☆ ★★★★☆ ★★★★★
Series 6000 (except 6082, 6061) ★★★★★ ★★★★★ ★★★★★ ★★★★★
6082, 6061 ★★★★★ ★★★★★ ★★★★★ ★★★★☆
Casting alloys Hardness Wear resistance Corrosion resistance Max thickness
Alloys with Si>8% or Cu>2% ★☆☆☆☆ ★☆☆☆☆ ★☆☆☆☆ ★☆☆☆☆
Die-casts with Si<8% or Cu<2% ★★☆☆☆ ★★☆☆☆ ★★☆☆☆ ★☆☆☆☆
Other alloys ★★☆☆☆ ★★☆☆☆ ★★★☆☆ ★★★☆☆
Coating thickness
Standard thickness Tolerance
50µm ±10µm
Treatment thickness grows 50% outside and 50% inside the surface of the aluminium piece. The radial dimensional increase is therefore equal to half the treatment thickness. 
Uniform thickness over the entire external surface. Reduced thickness in holes.
Aesthetic appearance
Slight matt appearance with dark grey colour. The colour tone depends on the base alloy and treatment thickness. Morphology is similar to the machined piece.
Black colour option in OX-HC version
The OX-HC treatment features extra layer hardness. This depends on the type of treated alloy.
Hardness value Alloy
>280HV Series 2000
>330HV Series 5000 (with >2% Mg) and 7000
>400HV Other wrought alloys
Wear resistance
OX-HS has very high abrasive and adhesive wear resistance. This varies according to the type of treated alloy.
Wear value, TWI-CS17 Alloy
A low number indicates a better performance – MIL-A-8625F and ISO 10074 C.3 – Taber Abraser wear test – abrasive wheels CS 17 – load 1 kg
<35 mg / 10000 cycles Series 2000
<25 mg / 10000 cycles Series 5000 (with >2% Mg) and 7000
<15 mg / 10000 cycles Other wrought alloys
Friction coefficient
The OX-HS-PTFE variant consists of an impregnation treatment of the anodizing layer with PTFE nanometric particles.
This impregnation permits obtaining a non-adhesion, self-lubricating surface with low friction coefficient.
Corrosion resistance
The OX-HS treatment permits obtaining high corrosion and oxidisation resistance. Brilliantly withstands 336 hours of exposure to salt mist without any sign of corrosion.
Corrosion resistance value Base material
NSS according to ISO 9227 and ISO 10074 10
≥336 hours without corrosion Alloy 6000
Chemical resistance
Approximate values of compatibility with the coating environment. The actual resistance to the environment must in any case be tested in the field.
Hydrocarbons (e.g. petrol, diesel fuel, mineral oil, toluene)
Alcohols, ketones (e.g. ethanol, methanol, acetone)
Neutral saline solutions (e.g. sodium chloride, magnesium chloride, brine)
Diluted reducing acids (e.g. citric acid, oxalic acid)
Oxidizing acids (e.g. nitric acid)
Concentrated acids (e.g. sulphuric acid, hydrochloric acid)
Diluted bases (e.g. diluted sodium hydroxide)
Oxidizing bases (e.g. sodium hypochlorite)
Concentrated bases (e.g. concentrated sodium hydroxide)



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