Chrome-plating goes inside the box

Citation

(2003), "Chrome-plating goes inside the box", Anti-Corrosion Methods and Materials, Vol. 50 No. 4. https://doi.org/10.1108/acmm.2003.12850dab.001

Chrome-plating goes inside the box

Chrome-plating goes inside the box

Keywords: Chrome, Plating, Corrosion

Chromium plating on steel produces a wonderful combination of surface resistance to corrosion and wear. These factors make chromium-plated bar the material-of-choice for hydraulic piston rods. But, there is a dark environmental side to the electrolytic plating process. The conventional arrangement – dipping batches of steel into open vats of heated chemicals – generates fumes that are dangerous to humans. As a result, the EPA requires venting of the entire building in which the process occurs, and the wastewater from the plating tanks calls for special treatment.

In more than a quarter century of chromium-plated bar production, Italy's Stelmi S.p.A. has developed a different approach to the process. Stelmi's unique equipment applies plating to bars as they travel horizontally through car – sized, closed and ducted chambers. An automated hydraulic-powered material handling system drives and rotates the bars one-by-one, end-on-end, through circular anodes insidethe chromium-plating machine. (The handling system also transfers the electrical contact to each bar.) Ground- and-polished bars enter from one side of the chamber and exit fully plated from the other. Plating covers the bar's surface right up to the ends, unlike the conventional process.

Employees are not exposed to open vats or tanks. The bath volume is one tenth of that required for comparable conventionalplating equipment and has no waste-water discharge. The closed-loop system incorporates redundant containment arrangements to eliminate risk of leaks or liquid spills. Overall, the Stelmi equipment has environmental controls that are well in excess of industry norms.

In addition, bars pass through the center of the round conforming anodes – instead of merely being placed near straight anodes. The result is the greater uniformity and better concentricity of the chromium layer, with the eventual plus of longer service life from the seals in dynamic contact with it. The homogenous layer has a microcracked structure that adds to corrosion resistance.

Manufacturers of conventional chromium-plated bars enhance their products' corrosion resistance by buffing the surface with various types of wax. Stelmi hard-chrome-plated bars offer superior corrosion resistance without any extra temporary coating.

Stelmi America, Inc. will begin production in Marshall, MI, near the end of the first quarter of this year. Three grades of plating will be available: Stelmi 200, 500, and 1000 – with the numerals referring to ASTM B-11 proven hours of neutral salt-spray corrosion resistance. For more information, contact Steve Dodge, Managing Director. Tel: 269/781-6222.