Powder Coating Quality Control Has Many Facets
Like a fine diamond, quality has many facets – rigorous testing is one.
Unmatched durability and longevity despite extreme conditions has made Powder Coating popular with manufacturers of everything from agriculture machinery to home appliances. To guarantee that each customer receives the full benefit of powder coating, the technicians at S&B Finishing don’t leave quality to chance.
Powder Coating Quality Control Testing
Performing a comprehensive series of seven tests on each part moving through their shop, S&B Finishing goes above and beyond what’s done in the majority of shops across the nation.
Prior to coating, each part undergoes a five-stage washing process that includes iron phosphate and alkaline cleaning. Removing all contaminating substances including oil, grease and moisture on each part is critical to proper adherence of the powder coat.
In order to assure that each part is impeccably clean, technicians perform the water break free test after the parts pass through the washing process. This involves spraying deionized water on the part and observing how the water reacts. If it drops like a sheet, that signifies the part is free from any dirt and ready for powder coating, otherwise additional cleaning is required. (Water-Break test – ASTM F22-13)
Following the application and curing of the powder coat, five more quality tests are performed.
The first involves rubbing the coated part back and forth 25 times (50 passes) with a cotton swab soaked with MEK solvent which verifies that the part has been cured properly during its bake time. If any coating rubs off, the curing process will be redone with an adjustment in temperature and duration. (MEK Solvent test – ASTM D5402-15)
A uniform finish is a key attribute that sets a powder coated surface apart from a painted one. To check that the powder coat’s film thickness falls within the ideal range as measured in mils, technicians next perform a mil-thickness test. This is crucial because parts with a coat that is too thick take on an orange peel-like appearance while an overly thin film shows varying shades instead of the desired uniformity. (Nondestructive measurement of dry film thickness – ASTM D7091-13)
Thirdly, the coat’s level of glossiness ranging from what is termed high gloss to matte is tested to be sure that it meets customer requirements and expectations. (Specular gloss test – ASTM D523-14)
The next test rates the coating’s hardness in the same terms used for pencil graphite. To carry out the pencil hardness test, technicians try to scratch the surface with pencils of differing hardness held at a 45 degree angle to determine whether a coating features an H, 2H or 3H hardness. (Pencil Hardness – ASTM D3363-05)
Adhesion another unbeatable characteristic of powder coating, is guaranteed through the fifth quality test, the crosshatch test, which involves cutting vertical and horizontal lines into the coat with a knife or scalpel then trying to remove the resultant squares with tape. When no coating comes off on the tape that demonstrates excellent adhesion. (Crosshatch test – ASTM D3359-17 method-B)
Once a part has aced all the above quality tests, it must pass one final examination prior to packaging—a thorough visual inspection by one of S&B’s seasoned quality inspectors.
S&B Finishing’s quality processes leave nothing to chance and customers can feel confident that the product they receive will perform and last as expected.
“When our employee performs this final test, I can rest assured that our customers are receiving a part that will withstand the test of time—and it’s a good feeling,” comments S&B Finishing President Kenny Spielman.
In addition to comprehensive quality testing, learn about S&B Finishing’s ISO 9001:2015 Certification.