Micro Crack Hard Chrome

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Using the HEEF 25 Process by Atotech :
                                                                      The Atotech HEEF 25 hard chromium process has been in existence for a number of years and was designed as a high speed, etch free replacement for ordinary chrome solutions. There are however many advantages for both the plater and end user by using this type of chromium. By depositing HEEF 25 the corrosion resistance properties are enhanced for the more demanding atmospheric conditions. This information sheet explains, in detail, the advantages.
General Description:
                                            HEEF 25 Features:  Micro cracked deposit minimum 1000 cracks per linear inch. Vickers Hardness 950 1150. Increased corrosion resistance. Increased wear resistance.Less edge build up and improved distribution.
                                                            HEEF 25 micro crack hard chrome has the features mentioned above. The main advantages to the engineer are the wear resistance, low co-efficient of friction, and in certain applications corrosion resistance. Plated products and processed components using the HEEF 25 are used in all types of engineering applications: Hydraulic Ram Rods, Linear Bearings, Pneumatic Rods, Gas Springs, Shock Absorbers, Shackle Pins, when the conditions demand a level of corrosion resistance beyond the normal performance of conventional bath. Such applications include underground mining, dockside and seawater environments.

Wear Resistance :

HEEF 25 has excellent wear resistance, far better than any of the alternative hard chromes. The test for wear resistance used is the FALEX WEAR TEST. This involves scratching the surface at a force of 750lb for 5 hours and measuring the loss of material.

The following results are typical.

HEEF 25 9.0 mg

Fluoride Catalyst Chrome 14.7 mg

Conventional 16.8 mg

HEEF 25 has almost twice the wear resistance of conventional micro crack hard chrome. The effect of the micro cracks improves the corrosion resistance.. In a conventional hard chrome the corrosion between the coating and the substrate escapes through the limited number of cracks, and if the corrosion rate is high the corrosion will cause large blisters of rust pushing the chrome away from the surface as the products of corrosion take up more space than the original material. With the micro crack coating the corrosion has many more routes of escape and the damage caused by corrosion is significantly reduced.

Corrosion Resistance HEEF 25 on Steel Substrate :

The resistance to corrosion depends upon the condition of the substrate and the thickness of the deposit. In general terms where a flash chrome deposit is specified i.e.: 20 30 microns, the common resistance is very dependent on the surface preparation and condition of the substrate. A poorly prepared surface coated with HEEF 25 will not be much better than an
equivalent coating thickness of a conventional macro crack chrome. When the surface is prepared carefully to defined surface conditions, the coating of HEEF 25 becomes far superior in its resistance to corrosion.

HEEF 25 Micro Crack Hard Chrome :

HEEF 25, as with any hard chrome plating has a low coefficient of friction, an important factor for cutting or sliding applications. To slide a chromium plated block of steel across a cast iron surface requires approximately 30% of the force required to slide an unplated block of steel across the same cast iron. Chromium plated surfaces tend not to seize, gall or cold weld themselves to another metal under mating conditions.

Surface Hardness :

HEEF 25 as deposited has a surface hardness of 950 1150 Vickers which is significantly harder than a conventional hard chrome of between 600 800 Vickers, thus resulting in improved wear resistance.

Structure :

Micro Crack Hard Chrome is so called because of the structure of the deposit. As the electroplating process takes place the Chromium being deposited becomes highly stressed. At approximately 2 microns deposit the coating cracks and continues to crack throughout the cycle time at 2 microns deposit. The cracks are not continuous to the surface. The number of cracks per linear inch will be a minimum of 1000.
 

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