Zinc arc spray keeps your aluminium tubes working longer
First, you need to consider a few things before going out and choosing the surface treatment for your aluminium products. You need to look at the type of material, method of processing, design, intended use and application. Because all these factors have an impact. Each has an effect on the lifetime and performance of HVACR equipment.
Coatings give you additional protection against corrosion and abrasion. Several types can be applied on aluminium tubing during the manufacturing process. Zinc arc spray is one of the alternatives.
Effective corrosion behavior from zinc arc spray
Putting a zinc layer on top of an aluminium alloy protects the core of the tube by providing a preferred path for corrosion to spread.
Zinc is a less noble element compared to aluminium alloys. As a result, it acts as a sacrificial layer guiding corrosion along the surface of the tube instead of through the wall of the tube. This corrosion behavior will lengthen the lifetime of the tube.
Zinc arc spray for round aluminium tubes and MPEs
The zinc arc spray process is commonly used on multi-port extruded tubes (MPEs) in the 1xxx and 3xxx alloy series, when assembled and brazed into a component used together with clad fin and clad header.
With zinc arc spray, an even coating with a good metallic bond is formed on the MPE. This zinc layer will diffuse into the micro-channel tube core during brazing.
Zinc arc spray coating is also used on round aluminium tubes, followed by a dedicated diffusion annealing. This lengthens the lifetime of the tube over an equivalent bare tube when tested in a SWAAT corrosion test.
I’d like to mention that de-bonding of the fins and tubes could be a negative side effect of using zinc arc spray. Avoiding excessive zinc spray load will eliminate this effect.
Interested in learning more?
If you are interested in learning more about aluminium tubing for HVACR applictions, then please contact Sapa and we will put you in touch with the right expert.