A particular coating for aluminium alloys allows the construction of lightweight and easy-to-clean sewer inspection systems.
Around the clock, worldwide, waste water is produced, flowing through widely ramified drainage systems to sewage treatment plants.
Constant monitoring and maintenance is required to ensure that the sewers are absolute watertight and passable. For approximately 50 years, camera systems have been used to inspect the sewers. These have been improved several times over the years.
Europe’s leading manufacturer of sewer inspection-systems uses aluminium materials to produce integral components for specific inspection carriages. These materials are easier to machine than ferrous materials and the carriages are therefore easier to transport and handle because of their relatively low weight.
The camera carriages are fed in the supply pipe via flexible plastic tubing, fitted with an internal cable for the camera and a fibre optic rod. This procedure causes substantial wear of the aluminium casing and the other components because of the abrasive movements against the pipe walls, as well as the soiling and corrosion by the residual waste water.
Such wear demands a suitable coating of the casing and other aluminium components. In this case, a 45 µm thick hard anodic layer, called HART-COAT®, has proven to be the best.
The coating is formed by anodic oxidation in a cooled acid electrolyte where the surface of the aluminium base material is converted into an aluminium oxide layer. This oxide layer grows equally inwardly as outwardly, creating a specific change in dimension of the component. It has a very good bond with the base material from which the layer is generated. This bonding is based on atomic binding forces.
The hardness of the aluminium oxide grants high wear resistance to the layer and to the aluminium casing. In order to facilitate cleaning procedures and to achieve a rolling-off like mercury droplets of the cleaning liquid, the HART-COAT® layer has embedded PTFE lubricants.
The good optical characteristics of the camera carriage in use in general public are not to be underestimated and this is substantially achieved by the coating.
