Today industrial parts manufacturers frequently perform surface treatments to alter the exteriors of finished metal components in order to obtain desired surface qualities. For instance, a company may seek to create parts with a more aesthetically pleasing appearance.
One popular type of additive surface treatment, galvanizing, assists in delaying the development of rust. It supplies a protective coating, usually zinc, over the surface of a metal workpiece. This process helps produce attractive, reliable metal products with longer anticipated useful lifespans.
The Galvanizing Process
During galvanization, a workpiece composed of iron or steel (or other metals) typically receives an exterior coating of zinc. This tough, brittle outer layer serves as a physical barrier reducing the impact of weathering on the interior. Galvanizing also offers cathodic protection against some corrosive processes. Manufacturers have developed a number of ways to galvanize metal parts effectively for industrial fabrication purposes.
Although a galvanized metal part exposed to outdoor environments will eventually begin rusting, the application of a thin layer of exterior zinc during galvanization slows down this process considerably. The outer layer of zinc will typically corrode sooner than the underlying metal. As it weathers outdoors, zinc reportedly develops a protective patina.
Different Ways to Achieve Galvanization
Metal parts fabricators have devised several methods for galvanizing steel and iron components. Four have achieved widespread commercial use:
One of the most popular ways to galvanize steels, a manufacturer usually performs hot-dip galvanizing by first carefully cleaning the surface of the metal workpiece to remove dirt, grease and other debris which might interfere with the application of a zinc coating. Today this process frequently involves the application of chemicals, although some fabricators perform mechanical cleaning and still others utilize both cleaning methods. Then the surface of the workpiece typically undergoes the application of a reducing agent to impact oxidation on the exterior during subsequent heating. The manufacturer immerses the metal workpiece for a designated time period in a bath of hot, molten zinc. The coating covers exposed surfaces with a protective layer.
Generally used in conjunction with automation, pre-galvanizing usually occurs during the production of sheet metal rolls at steel foundries. The mill unrolls the metal through a cleaning solution and a flux before briefly passing the exposed surface quickly through a bath of molten zinc and then re-rolling the sheet metal back into a coil. Since zinc maintains a fairly low melting point, it will easily dissolve into or coat metals with a higher melting point. While this process potentially provides protection for coated sheet metal surfaces, subsequent cutting during parts fabrication will leave unprotected, un-galvanized edges exposed unless the industrial parts manufacturer in turn chooses to galvanize unprotected metal surfaces during finishing.
Electrogalvanizing constitutes an alternative method used during the production of sheet metal at some mills and it, too, typically occurs in conjunction with extensive automation. It deposits a protective coating of zinc on the surface. While the foundry may gain a high level of control over the thickness of the galvanized zinc exterior coating using this method, electrogalvanizing applies a much thinner uniform layer of zinc than pre-galvanizing. (Sheet metal products which require more extensive corrosion-resistance protection to withstand harsh outdoor environments sometimes benefit from pre-galvanizing instead.) During electrogalvanizing, the mill uses an electrolyte solution and an electrical current to cause zinc to adhere to exposed sheet metal surfaces. The manufacturer must control the voltage and the time parameters closely during the ongoing production process. Once again, some sheet metal surfaces will display a lack of galvanization after cutting.
Also known as "thermal diffusion galvanizing", this modern process (resembling galvanizing) relies upon zinc powder to generate a protective coating including zinc covering the surface of iron or copper components. A manufacturer first prepares the surface of the workpiece to accept a zinc coating, often through the process of shotblasting. After placing the metal in a tumbler containing zinc powder, the fabricator applies rotation and heat. The moving metal parts contact the powder and emerge coated with a diffused, brittle protective layer containing zinc.
Materials And Applications
Galvanizing has achieved widespread use as a way to extend the anticipated useful lifespan of many metal products. Materials and applications sometimes vary based on production objectives.
Typically, manufacturers use zinc as a raw material for galvanizing. This element maintains a comparatively low melting point. Additionally, when covering steel, it will offer both a protective physical barrier and cathodic protection to the underlying metal. Galvanizing frequently results in the deposition of "spangle", tiny particles of crystallite material formed within the galvanized coating. By controlling production parameters closely, manufacturers can adjust galvanization to produce distinctive, visually interesting patterns on the exteriors of galvanized metals.
In addition to utilizing raw materials, companies engaging in galvanizing must obtain access to production facilities. These may include heated or electrified baths, close temperature controls and, often (at least in the case of sheet metal production), automation. The process of galvanizing has gained popularity around the world as a surface treatment.
Numerous applications exist for galvanized metal parts and components. Some of the most widespread include the galvanization of nails, automotive components and pipe products. Signage, fencing material, street lamps, and other metal items expected to remain in outdoor environments for extended periods of time may all benefit from zinc galvanization.
Advantages of Galvanizing
Galvanizing supplies numerous advantages. First, it helps enhance surface resistance to corrosion. By galvanizing metal products used outdoors, fabricators delay rusting. Second, this process helps reduce long term costs. It promotes more cost-effective product life-cycles. Finally, galvanizing offers aesthetic benefits. Consumers appreciate spangle's appearance.