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Metallizing for Corrosion Control Advantages of Metallizing

Metalizing is the most effective, long lasting protective coating available today. A metalized coating can outlast paint by a factor of more than two to one.

Can we be satisfied with the seven-year-old paint on the bridge pictured below? Is the value comparable with that received from the 1938 metalized coating on the Ridge Avenue bridge, which appears under our heading "Metalizing: The Effective Coating"?

Click here for bigger picture
I-71 overpass painted August 1992 with
zinc-paint-epoxy-urethane system. Photographed in 1998.

The entire coating process, blast cleaning, metal spraying and sealing is completed in one work day. Metalizing can be applied virtually year round and in nearly any shop or field environment. Metal coatings are applied during the summer in Houston and in the colder northern United States during winter months. Since ambient temperature does not limit metalizing as it does painting, the "coating season" may be extended by several months in most temperate zones. This permits key bridges, water tanks and other structures to be coated during low demand periods. Structures of virtually any size or shape may be metalized in a shop or in the field, and, remember, sprayed aluminum and zinc coatings contain no polluting volatile organic compounds (VOC's).

When deciding what material to apply to your steel structure, many factors must be taken into account. Among others, consider the following job specifics:

  1. Is the structure in a rural, industrial, or coastal atmosphere?
  2. What is the operating temperature?
  3. Is pH a factor? Is the structure subject to acid or alkaline or chemical attack?
  4. Can you achieve the required surface preparation?

Aluminum Wire

Sprayed aluminum is preferred for use in industrial environments, especially where there are high concentrations of sulfur dioxide and other pollutants. Arc sprayed aluminum has a relatively high bond strength even over marginally prepared surfaces.

  • Aluminum pH range is 4 to 11.
  • At elevated temperatures up to about 1100° F (590° C); for example, on the fire side of fossil fuel boiler tubes.
  • Applications include steel pilings above and below the mud and water lines; in marine atmospheres, offshore oil platforms, ship chain lockers, fish holding tanks; U.S. Navy applications are too numerous to mention.

Zinc Wire

Zinc provides greater galvanic protection than aluminum. Its greater galvanic power protects gaps in the coating better than pure aluminum. It is marginally easier to spray pure zinc than pure aluminum by some flame or arc spray systems.

  • Zinc pH range is 6 to 12.
  • Zinc should not be used in immersion service at temperatures above 140° F (60° C).
  • Applications include steel bridges, the inside of potable water tanks, power transmission and communication towers, buried iron pipe. Zinc is used in combination with galvanizing to avoid double dipping, and for general repair of galvanized steel.
  • A relatively new use for thermal sprayed zinc is for cathodic protection of rebar set in concrete. There are two types of systems which use the sprayed zinc; one relies on an impressed electrical current, and the other is passive or galvanic. This is a special application and requires a certain level of expertise. Call us with your questions.

Zinc Aluminum Wire (85/15)

Zinc - 15% aluminum wire combines the benefits of pure zinc with the benefits of pure aluminum in the metalized coating.

It is very often used as a substitute for pure zinc because it is somewhat more chloride and sulfur dioxide resistant than pure zinc, while retaining the greater electro-chemical activity of pure zinc.

Because it does not act exactly the same as either pure metal, certain guidelines for its use must be followed.

A metalized coating system is designed for a particular application and service environment. Commonly, a metal coating of .006"-.008" will provide very long service life. The metal coating thickness may vary so that a coating of .010" of zinc may be specified for the inside of a potable water tank, while a coating of .015" of aluminum may be specified for certain high temperature applications, such as valves and boiler tubes. In the case of structural steel, with a ten-year inspection cycle and minor periodic maintenance by re-sealing, a sprayed metal coating can provide an indefinitely long service life well in excess of 30 years. When maintenance is finally required, it may not be necessary to completely remove an intact metalized coating by abrasive blasting.

Metalizing may also be compared with hot dip galvanizing. The two metallic coatings are similar in some respects, but metalizing has some important differences. Pure aluminum and zinc-aluminum alloys may be sprayed. These coatings protect steel better than pure zinc in marine and industrial environments. Aluminum and the zinc-aluminum alloy, 85% zinc with 15% aluminum, are not available by hot dip galvanizing. When metalizing, the surface being coated remains at a low temperature, with local temperature never exceeding about 250-300° F. Because metalizing is a "cold process" when compared with either welding or galvanizing, there is virtually no risk of weld damage or distortion of the steel due to high temperatures or overheating.


Questions about any of our products or services?


We would be happy to help you- metalizing@metalizing.com.

Joseph T. Butler, Inc.
P.O. Box 173
Wadsworth, Ohio 44282
phone: 330-334-0262

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