INDUSTRIAL HARD CHROME

The electrolytic deposition of chromium to the surface of other materials, primarily metals occurs when electrical energy supplied to electrodes in a solution consisting primary of chromic acid is converted to chemical energy to produce chromium metal. Chromium is a desirable metal coating due to its inherent protective characteristics. A major application of industrial hard chrome plating is the salvaging of worn or mismachined parts where chromium is applied to restore the part’s original dimensions.

ADHESION AND BONDING

Adhesion between a chromium layer and the base metal upon which it is deposited is achieved by a molecular bond. Bond strengths in the excess of 35,000 psi are common.

CHROME PLATING IRREGULAR GEOMETRIC SURFACES

During electrodeposition, the current distribution over different areas of a component greatly varies, depending upon its geometrical shape. Elevations and peaks, as well as areas directly facing the anodes, receive a higher current density than depressions, recesses and areas away from or not directly facing anodes. The variation in current density over different areas produces a corresponding variation in the thickness of the deposited metal.

CHROME THICKNESS

There is no standard thickness for industrial hard chrome plating. Deposit thickness is generally dictated by economics and application performance. A thick deposit of chrome is of value when it provides additional wear surface.

CHROME WEAR RESISTANCE

Wear, defined as deterioration due to use, is affected by six major factors: impact, abrasion, non-galling friction, heat, corrosion and vibration. Chrome has three distinct characteristics that are advantageous in resistant wear: it is very hard, it is very slippery, and it is resistant to most industrially corrosive environments.

CORROSION RESISTANCE

Chromium is a hard, brittle, tensile-stressed metal that is effective in resisting most types of corrosion. As it builds in thickness, it develops a pattern of tiny cracks when the stresses become greater than the strength of the coating. These cracks form an interlacing pattern, which sometimes extends to the base metal. A corrosive liquid or gas could penetrate to the base metal. This can be prevented in three ways: a nickel undercoat can be applied to provide a corrosion-resisting barrier; the chrome plating can be applied to maximum thickness; or a thin dense chrome coating can be substituted.Click Here to view the corrosion resistance chart.