Test Methods Of Surface Treatment
NdFeB magnets contain rare
earth element neodymium, a kind of active metal, which is easily oxidized in
humid air. Therefore, NdFeB magnets are usually surface treated, such as
electroplating. For surface treatment, we have some test methods to check
whether it meets our requirements.
Coating thickness test
The thickness of the magnet
coating is directly related to the corrosion resistance of the magnet, and it
can also increase the compressive strength. Generally, we use a Plating Metallographic
Analyzer or a Plating Thickness XRF Instrument to test the thickness of the
coating.
SST and PCT test
Both SST (Salt Spray Test)
and PCT (Pressure Cooker Test) are reliability tests that evaluate the
functional reliability of a product during a specified service life under all
conditions (such as its intended use, transportation or storage) to maintain
its functional reliability. General SST test conditions are 35℃, 5% NaCl, Continual spray, and the test time is
determined according to the coating and customer requirements. The test
condition of PCT is 120℃, 2atm, 100%RH, and the test
time is determined according to the coating and customer requirements.
Adhesion test
The bonding force between
the plating layer and the substrate is also a criterion for judging the pros
and cons of the surface treatment. Generally, we use the one-hundred grid test,
which is to draw squares of equal size on the coating or plating, and then pull
them with a special tape, and judge the adhesion according to the peeling of
the coating (plating) layer.
Dyne pen test
Dyne pen test is also called surface tension test. Select the correct type of dyne pen according to the requirements, draw a line on the surface of the magnet and observe the surface change. If there is no obvious change on the surface within 3 seconds, the product is judged to be qualified.
Surface roughness test
The
surface roughness is closely related to wear resistance, the fit of mechanical
parts, vibration and noise, etc. It plays an important role in the service life
and reliability of mechanical products and is generally represented by Ra.
