Not all metal fabricators maintain in-house wet and powder coating operations, but it’s a practice that’s becoming increasingly more popular. Many fabricators will outsource coating to subcontractors and have done so in the past. While using a third party coating subcontractor can be convenient for the fabricator in some respects, the lack of control in quality and timeliness can sometimes compromise the delivery of parts to the OEMs that need them. A labor-intensive service, powder coating and wet coating are both staples of the metal fabrication process. OEMs expect aesthetic finishings that will last through even the most severe environmental conditions and now trust their contract partners have the expertise to apply them.
The Difference Between Powder Coating and Wet Coating
As the name suggests, wet coating is the application of a liquid paint to metal products as a finishing. This coating can be applied with a spray gun, pump or pressurized vessel. The metal must be thoroughly cleaned beforehand, which can be accomplished either with a solvent-soaked rag or pretreatment chemicals. Wet coating contains a carrier, which is typically a solvent, water or a mix of both. Wet coating is effective for products that can’t undergo the heating required for powder coating or those that require a color that can’t be matched with a powder coat equivalent.
Powder coating is the electrostatic application of free-floating, dry powder and does not require a carrier. Once the powder is applied, the parts are sent through an oven (at temperatures as high as 450 degrees), which transforms the powder into a liquid and eventually a solid coating. The powder coating process results in a thick final finish that is more durable than conventional wet coatings. Another advantage of powder coating is its speed, since recoating is generally not necessary. Powder coating is environmentally friendly and produces few harmful compounds. On the downside, thinner coatings are more difficult to apply.
What are the Environmental Concerns?
The solvents contained in wet coatings of the past were hardly environmentally friendly. They’ve since been replaced by faster drying coatings that don’t emit as many VOCs. Using water as a primary carrier has drawn skepticism because of its viscosity, according to The Fabricator, but waterborne coatings contain less harmful solvents. Powder coating emissions, on the other hand, are quite low and can be safely recycled.
What Makes a Quality Finish?
Coatings are quality tested so both the fabricator and the OEM can know its durability. Quality powder coatings, for instance, can achieve up to 3,000-hour salt spray test. The salt spray test is a strong indication of whether or not a coating can withstand harsh environmental conditions. This is especially true for equipment that will see most of its time outdoors, such as products in the agriculture, construction or oil and gas industries.
Working with a metal fabricator that has its coating process in-house, so they can effectively discuss coat quality and budget concerns, is invaluable. When this is done with a third party contractor, quality or timeliness isn’t always guaranteed. When coating is provided in-house, delivery is also expedited so parts are delivered quickly. If you haven’t already, discuss the prospect of coating with your contract partner in lieu of a subcontractor.