material precautions

Kynar coated powder coat finishes provide long-lasting protection against weathering, aging and pollution on architectural, commercial and residential buildings around the world. The sustainability of Kynar resins is unparalleled in the industry, however there are certain precautions that customers need to be aware of.

Flat Sheet. Be aware that flat sheet, leveled and sheared, may return to coil memory when baked in a cure oven, subsequently causing some tolerance issues.

Welded or stud welded attachments. Welded or stud welded attachments may cause flat sheet or break metal to distort when baked. Once distorted, the sheet or break metal may not return to its original shape when cooled. Welding will almost always cause distortion on aluminum sheet that will be noticeable after painting.

Assembled parts. Solution entrapment from the pretreatment process can be problematic to assembled parts. material that will carry water, must be drilled to allow drainage of the water in capture areas. It is recommended that customers make provisions for this prior to sending for finishing.

Enclosed tubes. Tubes with welded ends rarely are completely sealed and water will leak inside the tube. Enclosed tubes will require drain holes for the entrapped liquid.

Radius material. The heat from the baking process may distort radius material out of tolerance.

Extrusion Thickness. If extrusion wall thickness varies significantly on your project, color uniformity may be at risk. This is due to the differential in baking to reach the metal temperatures required to cure the paint. If a heavy walled extrusion is painted with a thin bead die, the bead die may over-baked, resulting in a darker appearance and lower gloss, as well as warpage of the metal.

Contaminants

Fisheye. Linetec's pretreatment system is not equipped to remove non-water soluble oils. These types of oils contaminate the system and cause "fisheye" problems with the paint finish.

Fisheye is a defect in the paint film appearing as a circular depression resembling a crater but not revealing bare substrate.

Corrosion. Storing metal outside prior to painting can cause corrosion that unless removed by sanding will cause staining and poor aesthetic quality.

Extrusion process residue. Residue from lead and wax used in the rolling process of tubes and extrusions will cause contamination problems if all if it is not removed. The lead and wax may run out in the baking process and cause damage to the paint finish and metal.

Faraday Cage Effect
Faraday Cage Effect

Faraday cage effect is the electrostatic force that prevents charged particles form penetrating into recessed areas. charged paint particles are attracted to the closest grounded surface, as shown.

Limitations due to an electrostatic painting system might make it impossible to achieve minimum recommended dry film thickness on all areas of an extrusion. Areas subject to the faraday cage effect are inside corners and recessed areas such as channels and cavities.

Faraday Cage Effect

The following criteria defines Linetec's acceptable quality level resulting from faraday cage effect.

If recess depth is from 50 - 100% of the width, there will be color coverage within the recess, but less than the specified dry film thickness.

If recess depth is from 100 - 200% of the width paint will be present, but the substrate may show through in some areas. The deeper the recess, the lighter the coverage will be within the recess. The substrate exposure will be less noticeable on pastel and light colors, and most noticeable on dark colors.

Recess depths greater than 200% of the width may not have any paint coverage at the bottom of the recess.

Material Racking Options
Racking for Paint application

The first stage in the powder coat application process is racking the material. Racking is a critical step; it ensures the automated spray bells and the painters can achieve good coverage on all exposed areas.

All material processed through the paint line requires some method of racking. Whenever possible, marks left from racking will be in unexposed areas.

Racking for Paint application Always let the applicator know if touch-up of rack marks are acceptable when it is required to rack on an exposed surface.

A one half inch border is required for racking of flat sheets. Clipping or hold punch are other options for racking of sheet material. The half inch border must be along the long side of the sheet when the dimension is greater than five feet.

Prints & Exposures

Up to date die drawings with accurate marked exposures is critical to a coating applicator.

Linetec defines an exposed surface (exposure) as the surface area indicated on a material shape that requires finish coverage. An exposed surface area, when assembled into doors, windows or other assemblies, is either viewable or in direct contact with environmental weathering.

When material is painted, accurate exposed surfaces must be supplied so rack marks can be kept to a minimum on the exposed areas whenever possible. Rework and double runs are minimized when accurate exposures are provided, thus minimizing the impact on lead times. The amount of paint in-house blended or ordered from the vendor is determined based off ff the total square footage of exposed surface areas.

Square footage, in most cases, is calculated based on a parts indicated exposed surface.

Calculation of a painted exposure, per lineal foot, is calculated using the exposed surfaces indicated on the print.

Exposed surface calculation may vary depending on the type of exposure, such as a single adjacent exposure on one profile or multiple non-adjacent exposures on the same profile. Exposed surface calculation may also vary depending on the material profile or type. Exposure calculations are subject to established minimums.

Primary Exposure is the exposed exterior and interior surface that must withstand the effects of the environment and normal use and wear. The primary surface must comply with all applicable AAMA specifications.

Secondary Exposure are semi-exposed areas requiring paint coverage, but which are not exposed to the direct effects of the environment or use and wear; this would include recessed channels and tracks. Semi-exposed, or secondary exposures, requiring paint coverage do not have to be in compliance of the AAMA specification. Minor blemishes such as runs and bubbles may be present and will not be rejected or touched up. Rack marks may be evident in secondary exposure areas and will not be touched up.



Powder coat project - during construction