Metallic Coatings Application Guidance

Precision Coatings metallic and iridescent performance coating systems provide special optical effect finishes that go well beyond standard architectural paints.  In using these high-performance coatings, consideration should be given to the surface preparation, equipment and applicator skills required to optimize application and performance of the coating system.  The following process description is designed to assist the commercial coatings contractor in assessing the time and costs that should be considered when estimating the application and material costs of applying special effects coatings.

The application of metallic and iridescent finishes on architectural structures in a field application is a multi-step process requiring a well thought out procedure, good application skills, ultra-violet resistant primers, specialty application equipment, consistent air supply and an expectation of a production rate that is a fraction of the rate typically used in the application of most opaque architectural paint products.  Metallic and iridescent finishes are translucent or clear resin systems with three-dimensional pigments that layout in a pattern that is dependent on the application technique employed by the applicator, the consistency of the air supply and steady flow of pigment through the gun.

Geometry of Substrate and Mock-Ups
Before the application of any coating, the geometry of the substrate must be considered.  Difficult shapes, angles and hard to reach areas that pose a problem for the applicator to keep the gun perpendicular to the surface must be assessed.  A plan should be developed to work with the geometry and a mock-up should be provided so all parties have the same level of expectation for appearance.  Consideration should also be given to not coating areas with metallics or iridescent finishes that will not be able to provide the desired special effects.

Primers and Base Coats
Metallic and iridescent coatings are translucent. As a result, in exterior applications, ultraviolet light will penetrate through the coating to the primer.  It is essential, therefore, that the primer or the base coat be able to hold up to ultra-violet light.  DTM 1300, DTM 1400, DTM 1600 and DTM 3000 are all designed to resist long-term exposure to ultraviolet light.  Conventional epoxies and alkyds should never be used for exterior applications under metallic and iridescent coatings unless an ultra-violet “blocking” coat is used as an intermediate coat.  The primer or the base coat should be applied over the entire substrate to achieve a consistent background color for the finish coats.  The color of the primer or base coat should be selected to enhance the finish coat given that the finish coat is somewhat translucent.  A gray primer is an excellent background for a silver metallic finish.

Air Supply
The constant flow of air in terms of volume and pressure is essential for the successful application of metallic and iridescent coatings.  The metallic flakes (aluminum) and iridescent chips (mica) layout in the resin system dependent on the way the coating is applied to the substrate.  Inadequate air volume or inconsistent air pressure will result in the misalignment of the pattern resulting in a splotchy appearance.

Application Equipment

Gravity Feed HVLP / Conventional HVLP Pressure / HVLP Turbine Sprayer
In the automotive refinish market where most manual applied metallics and iridescent coatings are used, the gravity feed HVLP gun is the choice of applicators.  The gravity feed gun delivers the metallic and iridescent pigments in an even and consistent manner as long as the cup remains primarily upright.  The advantage of the gravity feed gun is that the consistency of the metallic dispersion in the application stream helps to eliminate pigment striping that can be
experienced with  conventional HVLP pressure pot systems and HVLP turbine sprayers.  This is not to say that metallic and iridescent coatings cannot be applied effectively with a conventional HVLP pressure pot system or a HVLP turbine sprayer, but the use of such equipment can make the desired finish more difficult to attain.

Fine Finish Air-Assist Airless
Some good success has been noted by applicators using air assist airless fine finish equipment.  This type of equipment has proven to deliver metallic and iridescent pigments fairly evenly.

Roller application – requires special consideration
Some projects have been roller applied successfully (Please contact your Precision technical sales representative for recommendations).  The success of a roller application depends on the substrate and the size of the area being coated.  The level of expectation for the appearance of the rolled metallic or iridescent finish should be less than the comparable spray application.

Airless – not recommended
Commonly used architectural airless and industrial airless equipment are not recommended for the application of metallic or iridescent coatings.

The Applicator – The Most Important Role in Metallic Coatings Application
The most important component of a successful application of a coating system is the applicator.  A skilled applicator who understands the detail and precision required to successfully apply a metallic or iridescent three dimensional coating system is more an artist than a painter.  Success depends on staying in front of your work, keeping the gun perpendicular to the surface, moving into or away from the work to achieve the proper dispersion of the metallic flakes or iridescent chips in the coating film while maintaining proper orientation of the pigment.

Application of metallic and iridescent pigments is impacted by distance from the substrate.  The closer the gun is to the substrate, the more the pigment will bury in the resin system resulting in a darker and sometimes a deeper appearance.  The further away the gun is from the substrate the more the pigment will lie on the top of the coating resulting in a brighter appearance.  The same material applied by the same applicator the same day at different distances from the substrate can substantially change the color and appearance from the same gallon of metallic or iridescent coating.