The Limitations of Rack-Spray: Unfortunately, it isn’t for all components

Examples

Rack-spray coating requires what the name states – that every part is hung on a hook or inserted into a fixture. Because of this, there must be a place to “hold” the part.

With small fasteners, nuts, bolts and some stampings, this is not feasible. To hold a small fastener, it would most likely require being inserted into a cross bar of a fixture, ultimately completely masking one end and leaving it void of coating. And some small components do not have thru holes for a hook or, if they do, are too small.

In other instances, a thru hole (or trapped hole) could also be the contributing factor that inhibits a part from being rack-sprayed. For example, the part below has a threaded thru hole. The 8mm diameter is far too small and would prevent hardly any coating penetrating inside, ultimately leaving the entire center of the component void of coating. So even if there were quality issues or a surface finish requirement, this is not a component DECC could help with.

A bolt coated via dip-spin with a corrosion resistant coating

Tightly coiled springs are another problematic component that we cannot coat for two reasons. First, if a spring is too small, we would not be able to apply coating on the internal diameter due to the reasons above. Secondly, a spray method would not adequately build coating in between the coils and the part would not pass salt spray.

The last contributing factor that could prohibit a rack-spray application is price: if a part could be dip-spun and there are no finish requirements, we will usually provide a quote but also instruct our customer to seek out a dip-spin quote as well. Some parts could survive a dip-spin application, but would result in potential quality issues due to geometry. However, some customers only have a certain price point they can hit for outside processing and there are only so many things we can do that could reduce our price.