HART-COAT®

HART-COAT® is a coating developed especially for the functional improvement of aluminium materials (Hard anodising).

Coating takes place in a cooled acid electrolyte. In this case the workpiece is connected in series as an anode and oxidised in the course of the treatment. As a result of the oxidation the surface of the treated workpiece changes into a ceramic-like layer. This aluminium oxide layer is composed mainly of amorphous y-aluminium oxide, it takes the shape of regular cells vertical to the workpiece surface, encases the workpiece and protects the workpiece against wear and corrosion.

HART-COAT® is a functional aluminium coating, generally known under the term hard anodising. The properties of the HART-COAT® layer can be adapted to the type of material being treated by means of variable process parameters according to the specific requirements.

  • Wear resistance and hardness: the great wear resistance is due to the hardness and morphology of the aluminium oxide, which is alloy-dependent. The hardness that can be achieved by the HART-COAT® layer depends on the composition and structure of the base material and it varies between 400 and 500 HV 0.025.
  • Heat conductivity: the heat conductivity amounts to about 1/10 to 1/30 of the heat conductivity of the base material.
  • Temperature resistance: HART-COAT® layers can resist for short spans of time to temperature peaks of up to 2,200 K.
  • Electrical resistivity: The electrical resistivity amounts to 4×1015 Ω cm at 20°C, 0.8×1015 Ω cm at 100°C and 0.11×1015 Ωcm at 200°C.
  • Electric strength: The electric strength is alloy-dependent and it increases with the layer's thickness but not proportionally. The arithmetical mean value of 10 single measurements according to ISO 2376 amounts to 914 V with 30 μm of HC on AlMgSi1 and 1213 V with 50 μm of HC on AlMgSi1.
  • Colour: The colours with HART-COAT® range from grey-brown to black, with HC-CU from greenish grey to dark grey and with HC-GL layers from golden yellow to greyish yellow.

(All technical values published here are subject to the test conditions specified. We therefore emphasise that the applications and operating conditions, along with the end user’s practical experience, will ultimately determine the level of performance achieved by the coating and/or coating system.)

HART-COAT® is an especially versatile hard anodising coating. By means of various process variants it makes it possible to coat almost any aluminium wrought, cast and die-cast alloys.

HART-COAT® gives aluminium materials a wide array of functional properties. Thus the hard anodising coating allows the use of products made with these materials in the most diverse sectors.

  • Mechanical engineering
  • Metal fittings sector
  • Automotive sector
  • Mining
  • Office and data technology
  • Energy and reactor technology
  • Household appliance industry
  • Food processing industry
  • Medical technology
  • Measuring and control technology
  • Pharmaceutical industry
  • Defence sector

Overview of HART-COAT®- Process Variants


HCHC-CUHC-GDHC-GL
Variants For aluminium wrought alloys as well as sandcast and permanent mould cast materials For aluminium alloys with a copper content ranging from 2 - 6% For aluminium die-cast alloys with high copper and/or silicon contents For aluminium wrought, cast and die-cast alloys with moderate
contents of copper, silicon and lead.
Applications Pneumatic and hydraulic cylinders, advance levers, insulators, cylinder liners, hot plates or surgical instruments Pistons, valves, levers and rollers as well as centrifuges and cam plates Casings, gears, coupler
parts and cylinder heads		 For workpieces which require extremely smooth and corrosion-resistant surfaces

Post-Treatment

HC-PLUSHC-PLUS 2HC sealing
PTFE (polytetrafluoroethylene) is applied afterwards on the HART-COAT® layer and it improves the anti-friction and corrosion behaviour as well as the dry lubrication properties of the treated workpiece. The anti-adhesion property of HC-PLUS also facilitates the surface cleaning of the finished product. HC-PLUS 2 consists in impregnating an HC layer with PFA/PTFE. It improves the anti-friction and corrosion properties of the treated workpiece. In the case of abrasive wear the anti-friction properties of the coating remain unaltered. The HART-COAT® layer consists of aluminium oxide in the form of regular cells and each cell has a pore. The sealing of a coated workpiece is usually carried out in deionised water, generally without the addition of condensers, within a temperature range of 96 and 100 °C. This way the pores in the HC layer are sealed and the already good corrosion resistance is further increased.