The secret of BLACK

Black color is popular among DIARGE products, and this time we will introduce the surface treatment of metal products.

DIARGE's black color is expressed through surface treatment. There are two main types of surface treatment: plating and anion electrodeposition coating.

Only one item is coated with anion electrodeposition coating, so this time I will write about the plating that makes up the majority of the others.

Plating [plating = gold/metal gold]

How to read: plating

[noun] (sur)

1. [In ancient times, the gold amalgam used to plate Buddhist statues with gold was called nikin] To cover the surface of metal or base metal with a thin film of another metal. Also, something that did that. It is performed for corrosion protection and decoration, and methods include electroplating, hot-dip plating, and vapor deposition plating. Tokikin. “I’ll do it with money.”

2. To decorate one's appearance and make one look good.

Source: Digital Daijisen

[Types of plating used in DIARGE]

◇Dahl black plating

Wet rotary plating that forms a black layer on a copper base. It is characterized by its deep black color and powder-like texture. The black layer is relatively soft, and the plating has an aging element where the underlying copper gradually shows through the worn areas. It is also often used for bag fittings. DIARGE is designed for items that are subject to general wear, such as shoe horns and key rings.

Adopted items: 13304,13308,13316,13318,13327,13318,13329

◇Black chrome plating

Plating that forms a jet black, semi-gloss, uniform film with excellent adhesion, and is rust-proof, chemical-resistant, and wear-resistant. Among the many types of black chrome plating, we rely on partner companies that have unique patented technology.

Adopted items: 13315,13320,13322,13323,13324,13908

◇Black electroless nickel plating

This plating boasts the highest hardness among the black plating applied to DIARGE products. The Vickers hardness is equivalent to 220-280Hv, and it is not jet black, but more black than gunmetal.

Adopted items: 21000,21001

Depending on the purpose and shape of the product, we use multiple surface treatments, mainly for decorative purposes.

The question is, there is no black metal itself. However, why is it possible to express black through plating?

The secret lies in the relationship between physical structure and light reflection.

I think people have the impression that most metals are silver in color. Natural silver (Ag), the origin of the color name, has the highest reflectance of all substances, and is said to equally reflect over 90% of all visible light. A mirror is a glass plate with silver pasted on the back.

Conversely, the more light it absorbs, the darker it appears. Even if the material has the same reflectance, a small amount of light is absorbed every time it is reflected, so if the light is reflected repeatedly, it will be greatly attenuated, and no light will be recognized as reflected light to the outside. In other words, surface treatment can be said to reproduce black as a structural color by structurally absorbing light.

As an example, Vantablack, which is not plated but is made of carbon nanotubes, is a material that absorbs up to 99.965% of visible light. When light hits it, instead of bouncing it off, it is captured by a forest of tubes, refracted many times inside the tubes, and finally absorbed and diffused as heat.

In 2019, car manufacturer BMW improved Vantablack and announced ``VBX6'', which is the world's blackest car paint.

This is common to all black surface treatments, but because the surface is not smooth, it is said to be difficult to treat it with higher hardness and wear resistance than silver plating.

At DIARGE, we are proceeding with trial production of ion plating (physical vapor deposition: PVD) for some products in order to achieve higher abrasion resistance with black color.

We are working hard on research so that we can introduce it in the future. Please look forward to it.