Painting galvanized steel gutters seems to be a challenging task for most people. The real secret to painting galvanized steel is the surface preparation of the galvanized surface.
If the surface is newly galvanized, say less than 48 hours out of the zinc bath, the surface can be painted after a surface etching procedure. If the surface of the galvanized gutters has been exposed to the environment for more than a year, the surface can be painted after the dirt, grease and oils have been removed.
Paint peeling is common to galvanized steel gutters. The problem usually exists because unsuitable paint was used or improper preparation prior to painting the gutters and downspouts.
Hot dip galvanized steel has been around for many years. The value of hot dip galvanizing stems from the corrosion resistance properties of zinc, which is considerably better than iron and steel.
In addition to forming a physical barrier against corrosion, zinc, applied as a hot-dip galvanized coating, cathodically protects exposed steel.
Galvanizing for protection of steel is favored because of its low cost, the ease of application, and the extended maintenance free service that it provides.
Galvanized Steel is an excellent solution for Northern climates with snow and ice conditions. A strong and durable metal that contracts one half as much as aluminum.
Galvanized steel gutters are coated with a protective layer of zinc that helps to make the surface resistant to oxidation and rust. Unfortunately, this coating also makes the metal highly resistant to paint adhesion.
Paint will not adhere to any galvanized metal surface unless the surface has been cleaned and etched. You can etch galvanized steel gutters by coating them with a galvanized metal etching primer. Once the gutters are primed, painting galvanized steel gutters is easy.
Prior to painting galvanized steel gutters, the surface must be clean. The goal is to remove all dirt, grease or oils. Care must be taken not to remove too much of the galvanized coating. Alkaline cleaners, ammonia cleaners and solvent cleaners are the most common ways of removing dirt from a galvanized surface. Some cleaners may react differently with different painting methods so check with the paint manufacturer for any specific reaction problems.
For new galvanized steel, a water based cleaner can be used to remove oil and contaminants. Vinegar will also remove the oil coating on new galvanized metal gutters. Galvanized metal gutters over a year old, more than likely no longer have the machine oil on them. After cleaning, thoroughly rinse the surface with water and allow to dry.
Mineral spirits, turpentine, high flash naphtha, and other cleaning solvents can be used to clean galvanized steel surfaces if they are applied with lint free rags or soft bristle brushes. The rags and brushes must be changed often to prevent reapplying the contaminants. After cleaning, rinse thoroughly with water and allow to dry completely.
The cleaning solution can be applied by spraying or brushing. If brushing is used, apply the solution with a soft bristle brush, preferably of nylon,definitely not a steel brush.
Apply a coat of Galvanized Metal Primer such as Valspar professional industrial grade metal oil-based primer. Etching new galvanized metal is not necessary. Primers should be applied as soon as possible after cleaning. Allow the primer to dry completely.
Apply a coat of finish color paint over the top of the primer. Choose a paint with is compatible with the primer used.
DO NOT USE ALKYD BASED COATINGS when painting galvanized steel gutters. All galvanized steel has an oily film. If the film is not completely washed off (which it is almost impossible not to miss a spot) the aklyd coating will not adhere, creating a massive adhesion problem.
If your galvanized gutters have been previously painted and are having problems with peeling paint, be prepared to either strip them back down to the bare metal and start over, or be prepared to paint them on a regular basis. Scraping and priming will not re establish a bond in areas where the paint has not peeled yet. Applying primer and paint on your gutters at this point will not reestablish a good bond. It cannot penetrate through the existing paint and cause the defective paint underneath to re-bond to the galvanized metal. You will continue to develop peeling on these metal surfaces.
With the exception of some alkyd formulations, a variety of paint formulations have been effectively used for painting galvanized steel. Household alkyd enamels should not be used directly onto galvanized surfaces because the alkyd reacts with the zinc surface to form soaps which cause a loss of adhesion of the paint layer.
Some types of paint will not adhere adequately when painting galvanized steel or will only do so under certain conditions. In order to ensure a successful results, it is important to find a suitable paint with a primer coat that is fully compatible with a zinc surface. The first coat serves as a "tie coat" or interface between the galvanized steel and the topcoat.
Paint manufacturers should be consulted to provide specific guidance on the use of their products. Contact paint manufacturers for specific information regarding the suitability of paints for use on galvanized steel.
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