Through surface treatment,
we provide performance that cannot be obtained from materials alone.

DPI, whose strength is integrated production, performs surface treatments to meet performance requirements such as hardening and corrosion resistance. In addition to gas nitriding, which we can handle in-house, we can also handle plating, chromizing, and other treatments through cooperation with partner companies. Therefore, we propose optimal surface treatments that take advantage of the characteristics of each material.

Gas nitriding

It creates a nitride layer on the surface of the product and hardens to a specified depth from the surface. This treatment is performed primarily to improve wear resistance, and it is possible to improve the performance of the steel material without changing it. Gas nitriding can form a layer of nitrogen deep into the material. Therefore, a deep hardened layer is obtained.
As DPI has the equipment in its own plant, its vertically integrated production system can also contributes to shortening manufacturing lead times.

Ion nitriding treatment

Due to the gas nitriding, the product may change in size. Therefore, when strict dimensional accuracy is required, we propose ion nitriding. Although ion nitriding cannot harden to a depth as deep as gas nitriding, it has the advantage of less dimensional change and shorter processing time.


Plating is a technology that satisfies required performance by creating a film on materials. It has the advantage of having higher adhesion than paint and is less likely to peel off the surface. Various plating treatments are available depending on the required performance. We mainly use plating to improve rust prevention and corrosion resistance. Even relatively inexpensive materials can be improved in performance through plating.


It is a technology that hardens the material by creating a chromium layer on the surface, similar to nitriding. Chromizing does not provide the same hardness as nitriding. However, as materials have the property of becoming brittle as they become harder, chromizing may be appropriate depending on the application and required performance. Chromizing is also characterized by high corrosion resistance.


From design to manufacturing and quality control,
DPI will use its unique know-how
to meet your requests.

Inquiries TEL
03-5956-9175 (Parts business)/03-5956-9176 (Coupling business)
Business hours: 9:00 a.m. - 5:00 p.m.
(Excluding Saturdays, Sundays, holidays, and our company's holidays)

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