Measuring surface profile using the Elcometer 122 Replica Tape and Elcometer 124 Thickness Gauge
Before applying a coating, it is important to measure surface profile to ensure it meets the manufacturer’s specification. Creating an acceptable level of surface profile increases the surface area and provides an anchor pattern for the coating to adhere to, leading to optimised coating performance and efficient material usage.
Surface profile is a measurement of the peak-to-valley height of the surface.
One of the most popular methods of measuring surface profile is by using a replica tape, also referred to as a press-o-film, together with a micrometer thickness gauge, such as the Elcometer 124.
The Elcometer 122 Replica Tape consists of a foam pad attached to a non-compressible 2mil / 50μm mylar backing strip and provides a very easy method of measuring surface profile.
The Elcometer 122 replica tape is particularly useful when measuring surface profile of curved or hard to reach areas. Simply place the tape with the foam pad onto the surface and rub the backing with a burnishing tool (swizzle stick) until it turns uniformly grey.
Elcometer offers four variants of Replica Tape – ideal for inspecting different surface profiles. It is important that the tape grade chosen is reflective of the profile being measured.
How to use the Elcometer 122 Replica Tape
If you obtain a measurement which is at the maximum value of the tape (its range is written on each test piece for ease), select the next tape grade up and test again. Similarly, if the reading is at the bottom of the tape grade, choose the next grade down and retest.
Looking closely at the Coarse and the Extra-Coarse tape, you will see there is an overlap between 38-64 microns or 1.5 to 2.5 mils. If you measure a profile reading that’s between 38 and 64µm (1.5 and 2.5mils), a second measurement should be taken at the same spot, with the other tape grade. If both values are between 38 and 64µm (1.5 and 2.5mils) then the peak-to-valley height is the average of the two values. If the second value is outside this range, this reading should be used and the initial value discarded. This is displayed on the tape for clarity.
Once a replica of the profile is taken, use the Elcometer 124 Thickness Gauge to measure the peak-to-valley height of the surface profile.
How to use the Elcometer 124 Thickness Gauge
Using the Elcometer 124 Thickness Gauge is incredibly easy. To measure the surface profile, simply place the tape between the anvils of the gauge and gently release the lever.
The Elcometer 124 Thickness Gauge has been specifically designed to provide the correct anvil area and measurement force without affecting the profile reading. Using the value displayed by the Elcometer 124 Thickness Gauge, subtract the original thickness of the non-compressible mylar backing (2mil / 50μm) to get the surface profile measurement.
To get the most accurate reading, zero the Elcometer 124 Thickness Gauge to offset the original tape window thickness. The Elcometer 124 Thickness Gauge is available as either a metric or imperial model; and used in conjunction with the Elcometer 122 Replica Tape, provides an ideal method for measuring surface profile in compliance with International Standards. And if a permanent record of the surface profile is required, you can store the replica tape in your manual report as a proof of test.