HE Tubing MPE Coating solutions
Zinc (Zn) Arc Spray:
A Zn layer on top of aluminium provides a preffered path for corrosion to spread guiding it along the surface of the MPE instead of through the wall. This corrosion behaviiour significantly increases the lifetime of the MPE tube.
Zn arc spray is a process using electric arc to melt zinc wires and compressed air to spray the molten zinc on to the tube surface. It is commonly used on the MPE tubes in the 1xxx and 3xxx alloy series when assembled and brazed into a application used together ith clad fin and clad header. HE Tubing’s typical load of Zn on the MPE tube surface capabilities are between 5 – 14 gr/m2, depending on the customer’s requirement. This Zn layer wil diffuse into the micro-channel tube application during the brazing process. This Zn diffusion layer will provide good galvanic proteection during exposure to corrosive environment.
Different coatings that contain fluxing materials, zinc components and/or braze components like silicon particles or aluminium/silicon particles belong also to the capabilities (product portfolio) at HE Tubing. The Flux coatings are applied on the MPE tube surface in a separate production process after extrusion and before sizing and cutting the MPE to the Customers end specifications. Flux coatings can eliminate the need for fluxing and flux stations at the heat exchanger manufacturer production lines.
Since 2010 has HE Tubing a flux coating line in operation. A multi strand “state of the art” coating line containing a very precise roll coater machine that has the ability to apply a consistent thin coating layer on the aluminium substrate. Depending on the type of coating, a layer thicknesses between 8 and 35 gram / m2 can easily be applied.
HE Tubing produces coated materials according customer specifications which means that for each individual semi finished product the paint mixture has been developed, which makes it possible to achieve the best coating quality combined with the highest productivity. HE Tubing is using the finest components available in the market place in order to make this possible.
HE Tubings laboratory is well equipped to carry out all kind of supporting analysis and investigations on new developed coatings as well on existing coating recipes. In our laboratory we have a “lab-coater” that makes it possible to apply all typical flux braze coatings on laboratory scale. With the use of our braze oven a copy of the customers braze cycle can be simulated. Adjacent to this, SWAAT tests and metallographic analysis can be carried out in our laboratory as well. More deep analysis e.g. mapping of the coating components can be done with our SEM-microscope equipment.
HE Tubing has developed several types of coatings and together with the existing and widely used recipes HE Tubing can offer coating solutions to cover most, if not all of the applications.
The benefits of the use of a flux or braze coating is related to costs and environmental issues. The use of an applied braze coating reduces the number of production steps compared to the traditional process.
The difference between the traditional system and the “braze coating” system.
The advantages in costs are due to elimination of process equipment, possibly better utilization of the braze furniture (stacking of heat exchangers during brazing), precisely applied coating amount (no spill due to overspray), hardly any uncontrolled contamination of fluxing components with the environment and the possibility to apply zinc enriched components in order to create a galvanic corrosion protection during the same process.