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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.
If
you want to start a hard chrome plating
contact us
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