Spray wands are used in the pre-treatment stage of the powder coating process. They are used in wash stations to manually clean surfaces of items to be coated. Spray wands are used in small workshops that have a few surfaces to coat. Just like wash stations and blast rooms, spray wand stations are used clean, pre-treat, and rinse surfaces of all sizes, complexities, and configurations. Surfaces cleaned using spray wands have improved powder adhesion and durability.
Spray wands ensure that the surface is clean before the application process. They are mostly used to remove chemicals, solvents, and oil residues.
Spray wands use chemicals such as iron phosphate or detergents to clean the product surface. Steam or hot water is also used to clean. Phosphatizing improves metal adhesion and prevents corrosion. Spray wands are used in simple cleaning processes which involve one cleaning (phosphatizing) stage for small parts that do not call for corrosion resistance.
The spray wands can also be used in complex operations involving multiple cleaning stages and chemicals that provide better corrosion-resistant surfaces and ensures the durability of the coat through improved adhesion. The complex operations mostly involve the use of hot water or steam and chemicals such as iron phosphate. The spray wand used for this operations are advanced and can withstand high pressure. The process leaves a layer of phosphate on the surface, making it ready for powder coating.
Phosphates are used to clean surfaces that are moderately dirty. If the items to be cleaned are very dirty, the coater should consider other cleaning methods before cleaning with the chemicals.
Hand-held wands: Hand-held spray wands are used to clean manually. As opposed to automatic operators, manual operators can focus on stubborn stains and areas that are hard to reach.
High-pressure wands: These wands use hydraulic pressure to clean surfaces. Cleaning is done at pressures that range between 400 and 1000 psi. High-pressure spray wands can either use cold water or hot water (2000 F). Here, the operator can clean with or without cleaning compounds such as detergents or phosphates. Steam can also be used, but it is not as effective as hot water. Also, steam uses more energy than hot water.
The main advantage of using spray wands is they provide flexibility for angle as well as contact time. The disadvantages associated with spray wands include:
– They are limited to low volume work.
– They offer fewer chemicals for cleaning surfaces as compared to other spray washers. A phosphate coating converts the surface to an inert surface, thus improving bonding. The conversion also reduces the rate of oxidation in scratched surfaces.