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Common Appearance Issues in Liquid and Powder Coating

Applying spray or finish compounds is painstaking work, and there are often painful consequences for operators who don't take the time to do it right. There is little room for error when coating, especially in aerospace and other industries that have strict quality standards. Even small defects are usually unacceptable, so booth operators have to eat the cost of spot repairs or do a completely new coating when results are flawed.

Common Causes of Coating Issues

Workers and quality control personnel have to watch for several distinct types of appearance issues that may show up during or after the coating process. While the visible symptoms of coating issues are different depending on the type of compound applied, there are a few root causes that produce most of these issues.

Coating issues can be caused by:

  • Dirt Contamination
  • Surface Preparation
  • Problems During Application
  • Coating Composition

Dirt Contamination

Dust, dirt and other unwanted particles that get into the booth can contaminate the coating and jeopardize the entire process. One possible consequence are craters or "fisheyes" that expose the substrate through the cured film. This kind of flaw is easily visible and is almost always a failure in terms of usability. Contaminants can also cause bumps to form in the film as well as localized blistering or peeling. Any kind of lubricant, oil or liquid on the surface of the material can be a big problem.

Surface Preparation

Before parts or products enter a spray booth, they are usually prepared through physical and chemical treatment as needed. It's important for operators to pay attention to all the details of pretreatment to avoid costly coating issues later on. Both liquids and powders are specifically formulated to bond with defined substrates in a certain condition. Proper preparation may require cleaning the entire surface and grinding down bumps, residue and any visible markings prior to finish applications.

Problems During Application

When spray coatings are as rough as the peel of an orange, then workers may need to adjust how they handle equipment inside the booth. Pinholing, which describes tiny holes or indents across the coating, is another common application problem that results from using incompatible or dirty equipment. Staff should always work with clean, maintained and compatible equipment when in the booth. They also need to be trained to maximize efficiency and ensure personal safety through proper handling techniques.

Coating Composition

Liquids and powder coatings are both specially formulated through a delicate balance of potent and potentially-volatile compounds. These substances are sensitive to pressure, heat and humidity, so operators need to choose and handle their coating compounds carefully. Compounds need to have the same surface tension as the substrate or there is a high risk of unsightly runs or sags in the coating. Poor-quality resin can also lead to blooming and blushing, which are both types of visible discoloration across the surface.

Getting Over Appearance Issues in Coating

Shops plagued by recurring appearance issues have a serious problem on their hands, and ignoring it is rarely an option. Every defect has a discernible cause, but it's not always easy to figure out exactly what part of the process is responsible. As a leading provider of professional spray booths and solutions, Spray Systems is here to help our clients overcome appearance issues in their coating operations.


Sometimes the best way to get over constant coating problems is to contact professionals for advice and consider the options for transitioning to a new booth system. Spray and finish applications are vulnerable to a host of environmental hazards, operator errors and material flaws, so there's no substitute for a specialized booth that is designed and built by industry experts.

posted on Thursday, April 11, 2019