Black Galvanizing: What Are Its Characteristics

Black Galvanization: What Is It?

The term galvanization describes an industrial mechanism that serves to protect metals from galvanic corrosion, when two materials or two parts of the same material are exposed to different conditions and are placed in direct contact with each other, in the presence of a third element on both (the electrolyte).
The zinc coating thus serves to ensure that, in case of breaks or porosity of the protective surface, it will be the latter to be affected and not the metal object.
Among the different types of such processes, particular attention can be paid to static electrolytic galvanization.
In static galvanization, the metal pieces are hung on frames supported by bars. These bars are moved by an overhead crane while the pieces remain fixed.

During this industrial process, several preparation phases are carried out:

• Washing
• Degreasing
• Pickling.

Subsequently, zinc is deposited on the metal object through a processing cycle defined as "passivation".
Depending on whether the deposited zinc layer is chrome, basalt, or silicon, the finished piece acquires a different color:

• White galvanization
• Yellow galvanization
• Black galvanization

The black electrolytic galvanization process results in the black coloring of the metal. This result is obtained through black passivation combined with a sealing step that further improves the aesthetic appearance and corrosion resistance.

The main products that can be black galvanized are:
Self-tapping and self-drilling screws.

These types of screws are widely used in sectors such as window and door frames, furniture construction, mechanical constructions, joinery, and in the automation sector, albeit to a lesser extent.

It is important to specify that not all products belonging to the family of self-tapping and self-drilling screws are available with this treatment, and it is advisable to specify during the request and/or offer phase.

How is cold galvanization carried out?

Unlike hot-dip galvanization, which is used for its higher material protection capacity from corrosion, cold and thus black galvanization is mainly used for aesthetic purposes of the products.

The cold galvanization process is also called metallization and involves applying a resin-based zinc layer to the metals. It is, therefore, a real painting process that requires several processing phases.

Yellow Galvanization and White Galvanization

As already anticipated in the previous paragraphs, the layer of zinc salts applied to the metal determines its coloring. Indeed, besides black galvanization, it is also possible to obtain lighter colors, such as yellow and white.
But what is the difference between yellow and white galvanization?

• White galvanization is the process by which the object acquires an almost bluish color appearance. This passivation gives the material good corrosion resistance. The categories with white galvanized products are: high and low resistance hardware, nuts, washers, self-drilling screws, and lifting accessories.

• Yellow galvanization, also known as tropical, is that process of yellow passivation that gives the material excellent corrosion resistance. This processing allows for greater resistance to salt fog as well, an accelerated corrosion test that produces a corrosive attack and measures the suitability of the protective coating.

Among all the products subject to galvanization, there are some types of self-tapping screws (for example, screws for wood) that can be found both white and yellow galvanized, depending on the purpose of use and the consumer's need.

Given the wide use of these types of products, we refer to a rich and comprehensive assortment of screws and bolts with white or yellow galvanization.

Sectors of Use

Static galvanization and thus white, yellow, and black galvanization is used in various merchandise sectors working with metals. Among these, for example:

• Production and installation of frames;
• Furniture sector;
• Special mechanical processing.

Galvanization is, therefore, a process that, applied to metals or metal alloys, improves their appearance, durability over time, corrosion resistance, and brings numerous advantages, well listed in a previous article.

Specifically, as for black galvanization, the main disadvantage is the poor transmission to the material of corrosion resistance properties. This passivation, however, gives the object a particularly shiny appearance.

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