Natural finishes of various metals have differing characteristics. Copper is bright and polished when new, but quickly oxidizes to a deep brown. Fingerprints and surface scratches are quite conspicuous at first, but do the finish no harm, because they become invisible as the metal weathers. Still, it is customary when working with copper to wear cotton gloves to minimize fingerprints during installation. The material can be easily spot cleaned with an abrasive pad , or metal cleaner/polish. In contrast, bare “Galvalume” steel will retain fingerprinting indefinitely, permanently staining the finish. Most other staining from foot traffic, power cords, tools and such will also cause indelible stains. “Galvalume” should never be spot cleaned with any kind of abrasive material, nor any cleaners that contain strong alkali or acid. Pressure washing and mild soapy solutions are the sole remedies. “WD-40” and similar solvents, which clean most metals quite satisfactorily, will cause permanent staining of “Galvalume”. Fingerprinting will be minimized if installers wear gloves. Use of an acrylic coated material (“Galvalume Plus” “Zincalume Plus”) will be more effective in minimizing the effect of installation staining, than anything else the installer can do.
Other metals and finishes all have their own idiosyncrasies, which should be learned from their manufacturers or distributors.
Some paint types are more fragile than others, and often painted steel and aluminum surfaces are protected with a strippable plastic film. This film is applied during coil processing, and intended to help protect the finish during transit and installation. It is critical that the installer strip this film prior to prolonged exposure to sunlight, as it will become brittle and very difficult to remove after such exposure. Care should always be exercised in handling painted finishes and foot traffic should be minimized or eliminated, or surface scratching is almost certain to result.
In the event of surface scratching during installation, touch-up paints are usually made available by the panel system manufacturer. Discretion should be exercised in their use. Because they are often different resin types than the coil-coated material, they will weather quite differently. Although the color match may be perfect at the time of installation, the air-dried paint will fade more quickly and may be unsightly after a number of years. For this reason, they should only be used in the event of a severe scratch, and then applied only to the scratch itself, with a small artist’s brush or a “paint pen”. Remember that from an aesthetic standpoint, over use of touch up paint will be much more conspicuous than the untouched scratch in several years time. If surface scratching is excessive, the material should be replaced, rather than touch-up painted.
The same principals as stated above apply to the painting of other components to match prefinished metal panels and flashings. Most such paint applications will have very different weathering effects than the factory finishes, and will mismatch in a few years, even when the initial match is perfect. Whenever possible, use prefinished sheet metal flat sheets to color match other components and roof accessories, rather than air dried paints. Often this practice is also more economical, as the cost of field painting can be substantial.
Occasionally, a paint finish is used which is “directional”. Which means that the finish will reflect light differently from different angles, giving a different appearance. Metal flake finishes are usually directional. The installer must exercise extreme caution during installation of such finishes to be sure that the direction of the finish is consistent. Reversal of the finish direction may not be obvious at first, but quite consspicuous when viewed at a distance, and under different lighting conditions. Normally “directional” finishes are marked with arrows printed on the non-weather side so that installers can keep them consistent in installed direction.
It was discussed above that in the event that touch-up of the paint is required that either an small artist’s brush or a paint pen be used. Drexel Metals Inc. was the first to introduce such a tool (paint pen) for touch-up for metal roofs.
The Drexmet Paint Pen is the first of its kind in the industry and utilizes a Fluoropolymer Air Dry System. Developed with the contractor in mind, the Drexmet Paint Pen is the lower cost and more efficient alternative to other touch up systems. The Drexmet Paint Pen allows contractors to quickly and easily touch-up scratches on the metal panels, saving time, money and future potential problems. No waste, no spillage, no brushes, no cleanup. The Drexmet Paint Pen is available in all of our 30 stock colors and has a shelf life of up to six years.
For more information regarding paint finishes or any questions concerning standing seam metal roofing systems contact Drexel Metals at 888-321-9630 or visit us at http://www.drexmet.com
This article and others in the drexelmetalsretrofitroofing.wordpress.com Blog are written by
Bill Dooley, ASCE, CSI
Director of Architecture Sales Drexel Metals Inc.
Drexel Metals Retro Fit Roofing Blog 