Plating type: Hard chrome plating
Performance: High hardness
Industry: Water infrastructure
Product: Valve box

■ What is hard chrome plating?
Also called, "industrial chrome plating", "HCR", "ICr". When the film thickness is thin, it is called "flash plating" or "micron plating".
This is a typical plating process with many mechanical properties. (Industrial chrome plating JIS H8615) Very hard and has a small coefficient of friction that makes it wear coefficient and durable.

■ Principle of hard chrome plating
Chromium plating is a simple bath composition in which chromic anhydride (chromium trioxide CrO3) is the main component and a small amount of sulfuric acid is added as a catalyst root. Called the Sargent bath, it is widely used and developed by Sargent nearly 90 years ago. The standard weight ratio is Chromic anhydride: sulfuric acid = 100: 1.

■ Features
·Hardness
It has the highest hardness of all electroplating. The value changes from 750 to 1000 HV depending on the plating bath temperature and the cathode current density. It has long been recognized that a stable hardness of approximately 900 HV can be obtained with a cathode current density in the range of 15 to 80 A/d㎡ at a bath temperature of 55°C in a standard concentration Sargent bath.

・Abrasion resistance
It is the most important basic property required for hard chrome plating and is extremely good. The cause of metal wear is extremely complex, mostly due to the high hardness of the chrome-plated coating.

・The coefficient of friction is lower than other plating.

・Corrosion resistance
Stable against chemicals other than chloride.
A coating with a thickness of 10 μm or more even in the atmosphere shows relatively good corrosion resistance. Chemicals that erode hard chrome plating include hydrochloric acid, hydrofluoric acid, phosphoric acid, oxalic acid, dilute sulfuric acid, citric acid, lactic acid, and calcium chloride.

・ Hydrogen embrittlement
Hard chrome plating has a poor covering power, so it is necessary to devise the jig. The covering power gradually improves when apply base in the order of steel, brass and copper, and nickel.

・Has excellent lubricity. It's hard to stick with the friction mate.

・Hard chrome plating is non-magnetic.

・Heat-resistant
The film hardness gradually decreases from 200 °C to 400 °C, and decreases sharply above 400 °C.

・Adhesion
Since it is a bond (alloy) of metals, so it will not come off easily.

・ Overlay
For dimension correction/repair purpose, it is possible to obtain a large amount of film thickness. In our past cases, we can perform plating with a film thickness of 1 mm.

・Hydrogen embrittlement removal (baking treatment)
A method of releasing hydrogen by heat treatment. The general heat treatment conditions are 190 °C to 200 °C within 4 hours after plating and 2 hours or more.

・ Releasability (adhesivity)
Required feature for molds. It is closely affected by low coefficient of friction and slipperiness.

★ About Us
We have 13 various size plating tanks for hard chrome plating with maximum length of 7 m. We can handle various parts.

We are acknowledged for masking technology cultivated through many years of experience, and jig manufacturing technology to design and manufacture in-house. We can perform partial plating which is normally difficult.

★ We will response comprehensively. Please feel free to contact us!