Metal Maintenance & Cleaning
In keeping with our motto of "The perfect prescription for solutions to Buiding Headaches" we would like to pass on to you the following reprinted article. It contains good advice to help extend the life of metals roofs and wall panels.
From the Glidden Company
Keeping Metal Walls and Roofs Tip-Top
How to keep metal panels, especially roof panels, clean is a frequent question from planners. Some cities have even imposed maintenance ordinances for keeping standing seam metal roofs clean. Owners, themselves, often have a maintenance program for roofs and walls.
The following suggestion for cleaning metal walls and roofs are by J.F. Papenfuss, a nationally recognized authority from the Glidden Company, a leading producer of metal coatings.
Regular Maintenance Suggested
A regular exterior maintenance/cleaning program may be desirable in unusually dirt laden or aggressive environments.
Power washing with plain water may be adequate. When heavy dirt deposits dull the paint surface, a long handle soft bristle brush and a solution of water and detergent may be used in other situations it may be necessary to use a detergent solution in the power washer.
Suggested Cleaning Metals
Strong solvent and abrasive cleaners should not be used for factory painted panels.
A good basic detergent cleaning solution is 1/3 cup Tide® detergent dissolved in 1 gallon of water.
If black/green mildew is apparent, the above detergent solution should be modified as follows:
1/3 cup detergent (e.g. Tide®)
2/3 cup tri-sodium phosphate (e.g. Soilex®)
1 quart 5% Sodium hypochlorite solution (e.g. Chlorox®)
3 quarts of water
There is not enough room here to list all the possible cleaning detergents, solutions or procedures. Consult maintenance professionals and/or label instruction for proper handling and disposal of washings. However, the last and very important step in any cleaning procedure should be thorough rinsing with clear water.
It is also advisable to test any cleaning procedure on a representative, small area for the desired results before working on a larger scale.
Caulking compounds, oil, grease, tar, wax and similar substances can usually be removed with a cloth dampened with mineral spirits. Spot clean contaminated areas only. Again, since different paint finishes show different solvent sensitivities, test a small area first. Follow any solvent cleaning procedure with a water-detergent washing and thorough clear water rinsing.
Maintenance of Exterior Finishes on Factory Painted Steel Sheets
This section pertains to high quality coatings applied to galvanized steel in coil form and baked at high temperatures to give durable, tough, flexible finishes. The steel sheets supplied to you by Colorstrip are made by this process and are coated with these high quality, modern finishes.
Galvanized steel has many good properties as a substrate for painted building sheets. The zinc coating acts as an effective barrier to corrosion and provides proven sacrificial protection at cut edges, scratches and drilled holes. By cathodic action, the zinc builds up a light colored corrosion product on exposed edges and provides a protective layer, which prevents corrosion of the steel base of the panels for very long periods of time. With this protection, pre-painted sheets do not show red rust stains from the steel base even if the paint coating is scratched, or cut edges are exposed.
To further improve the quality of the pre-painted steel, a rust inhibitive primer is used under all finish coats. This primer coating promotes improved adhesion and further increases the corrosion resistance of the coating system. It also permits the use of finish coats especially formulated to give the best in color and gloss retention and chalk resistance on exterior exposure.
Proper installation and maintenance are very important in obtaining the very best results from the use of prepainted steel sheets. The following information should be read carefully before engaging in any of the operations listed under the three headings of (1) Installation and Storage, (2) Cleaning Paint Surfaces or (3) Refinishing Prepainted Steel Sheets.
Pre-painted formed sheets must be protected from moisture until erection on the building. Proper packaging and storing procedures should be followed. Otherwise, a white storage stain may appear at exposed edges and at cracks in the paint. If waterproof covers are intact, bundles of sheets may be temporarily stored at the building site but should be slanted to provide proper drainage of any moisture condensation. Damaged packages should be protected from the weather.
Proper handling and stacking should be observed in transit to prevent abrasions. During installation an important cause of damage is the dragging of whole sheets, or edges and corners across other sheets. Here the sacrificial action of the zinc coating will prevent rusting even if both the paint and galvanize coatings are cut through. If the appearance is damaged sufficiently, a touch-up operation may be necessary. (See the section on touch-up under (3) Refinishing).
If additional forming operations are necessary the metal should be warm. A minimum metal temperature of 90°F should be obtained for mild forming and 120° to 140° for severe forming. A suitable wax may be used for improved lubrication. Note: Care must be exercised in stacking waxed sheets due to the increased slipperiness.
The fine cracks in the paint and the zinc coating occur when tight bends are formed regardless of the source of the hot-dipped galvanized steel. The zinc tends to crack beneath the paint to cause a fracture in both coatings. These small cracks are not necessarily harmful since the adjacent zinc protects the breaks from red rust.
Improper cutting and drilling of prepainted sheets can cause bad rust spotting. Hot chips from drilling operations or from saws or cutting discs, may embed themselves in the paint. Even though the sheets themselves are not cut, chips rust and form unsightly red spots on the painted surface that may become larger than the original chip. Shearing is recommended to eliminate this problem wherever possible. When saws, drills, or cutting discs are used, the paint should be protected with a plastic cover. In some cases, pre-painted sheets can be turned over while being cut so that the ships will fall on the inside surface.
Though the factory applied finishes for hot-dipped galvanized steel sheets are so durable they will last many years longer than ordinary air dry building paints, eventually it may be desirable to thoroughly clean or repaint.
Dirt pick up may cause apparent discoloration of the paint when it has been exposed in some dirt-laden atmospheres for long periods of time. Slight chalking may cause some change in appearance in areas of strong sunlight. A good cleaning will often restore the appearance of these buildings and render repainting unnecessary. An occasional light cleaning will help maintain good appearance.
In many cases simply washing the building with plain water, using hoses or pressure sprays will be adequate. In areas where heavy dirt deposits dull the surface, a solution of water and a detergent (1/3 cup Tide® per gallon of water for example may be used. A soft bristle brush with a long handle may be useful. A clear water rinse should follow.
Mildew may occur in area in areas subject to high humidity but is not normally a problem due to the high inherent mildew resistance of the baked finishes used. However, mildew can grow on dirt and spore deposits in some cases. To remove mildew along with the dirt the following solution is recommended:
1/3 cup detergent (Tide® for example)
2/3 cup sodium phosphate (Soilex® for example)
1 quart sodium hypochlorite 5% solution (Clorox® for example)
3 quarts water
Solvent and abrasive type cleaners should be avoided. Caulking compounds, oil, grease, tars, wax and similar substances can be removed with mineral spirits applied only to the areas, which are contaminated. Follow up the use of solvent with detergent cleaning and rinsing.
3. Refinishing Prepainted Steel Sheets
To refinish installed steel sheets, either after prolonged weathering or when relatively new, the following procedures should be followed.
The surface should be thoroughly clean and dry. Follow the cleaning practices given in section (2) Cleaning.
High gloss areas should be sanded with No. 4 or No. 6 sandpaper.
After the cleaning operations, the surface should be allowed to dry completely. Bare metal surfaces should be spot primed and air-dried overnight or in accordance with the manufacturer's directions. If wax is present on the surface, cleaning with a solvent such as mineral spirits may be necessary.
For the finish coat, a good grade of commercially available air-dry auto paints are recommended.
The refinishing should not be done on rainy or windy days.
This section provides only general guidelines for refinishing operations on most of the coatings applied.
