Commercial zinc in the name or label given to a zinc finish specification that is commonly used in finishing metal parts. When specifying "commercial zinc", you get a basic range of zinc finish protection. The normal composition has a thickness of .0002" (two ten thousands of an inch) of zinc applied by electro-plating. Some commercial zinc formulations add a chromate top covering to protect the zinc finish. The commercial zinc finish applied by A. L. Hansen Mfg. Co. includes the chromate top covering.
Even though zinc provides protection from rust formation, the surface of the zinc does not remain bright or stain-free in use. To avoid staining and provide some abrasion protection, a thin film of chromate is applied over the zinc finish. There are 3 classes of chromate finishes in general use: blue bright, clear and iridescent color (yellow "gold", black, olive drab). The protective value of a chromate finish increases with increase thickness.
Yes. The American Society for Testing Methods (ASTM) specification B633 has four classifications for electroplated zinc finishes. They are based on coating thicknesses and type of application / environment that will be seen. Service conditions 1 is mild indoor applications and they move up to service condition 4 which is very server exposure to harsh outdoor high abrasive applications. The basic idea is that protection increases as the finish thickness increases.
That depends on the level of protection you are seeking for the intended application. In a highly corrosive salt water environment, like a boat, a commercial zinc finish is not normally used. That is why you see more expensive powder coat or chrome finishes. Commercial zinc is normally used for indoor applications or as the base coat for a more protective top coat such as paint. Again, finish protection normally increases with increasing thickness.
Salt spray testing is a means to measure the relative protective value of a particular finish. The keyword is relative. By rigidly controlling the exposure enviroment, a value can be derived to measure when corrosion starts. The American Society for Testing Methods (ASTM) salt spray specification B 117-90 is a detailed testing method for controlling the amount of salt spray solution, at what temperature, in what direction and much more. The results, normally in hours of exposure, allows for comparison of different finish formulations.
First is knowing your application/environment requirements. What life do you expect from the finish and how should it look after 1, 3 or 5 years. The finish protection required for outdoor road use is greater than indoor office use. There are a number of finish combinations (zinc, zinc = paint, powder coat, e-coat) that provide extended protection. Work with your component supplier and learn what finish options are available for your application.
Yes. More material and time is needed to achieve increased protection. However, a good manufacturer will make sure to only apply the necessary finish needed for your particular application. These will ensure you pay only for what protection you need. (See comment above)
A. L. Hansen Mfg. Co. provides a wide array of finishes for a number of applications. They range from commercial zinc to custom color powder coats. Also, we meet very stringent & specific customer and government finish specifications for some complex assemblies. as a company, we are continuously investigating new finish offerings to increase our knowledge about protection. Our goal is to provide a wide selection of cost effective finish options so our valued customers can get the maximum service life from our quality products.
If you have any additional questions not covered here, feel free to contact us via e-mail at: firstname.lastname@example.org , by phone at: 847.244.8900 or at the following address: A. L. Hansen Mfg. Co. 701 Pershing Rd. Waukegan, IL 60085