Silicon Carbide; Zirconia Alumina; Diamond Sanding Paper; Safety Rules - Thermo Scientific XL2 User Manual

5
Common Operations
Metal Sample Prep

Silicon Carbide

Zirconia Alumina

Diamond Sanding Paper

Safety Rules

58 Niton XL2 Analyzer User's Guide
Aluminum oxide is the most common abrasive surface used today. For most applications it
will be safe to use aluminum oxide discs. But if test results for aluminum in any metal alloy are
significantly higher than expected, switch to another type of abrasive disc. Also, when
grinding aluminum, aluminum oxide discs tend to trap aluminum from the metal surface into
the disc surface. Once this happens, the disc looses its efficiency and cross contaminates the
next sample.
Silicon carbide discs are a good alternative for aluminum oxide and the cost of a disc is only
slightly higher than aluminum oxide. This adhesive type is best for grinding aluminum,
copper and other soft metals.
Zirconia alumina discs are more expensive than aluminum oxide or silicon carbide but they
last much longer and so may be the best investment. Few metal alloys have low additive levels
of zirconium, so it is one of the safest abrasive types for general use.
One exception is the Aluminum alloy Al 7050 which is a near twin to alloy Al 7075 except for
the ~0.1% Zr in 7050. Therefore, if 7075 is ground with Zr grinding paper it may be
erroneously identified as Al 7050 due to the Zr transferred from the grinding disk to the
surface of the Al 7075. s
Do not use diamond sanding paper for surface preparation in the field. Even after extensive
and aggressive sanding with diamond paper, a metal surface will not be prepared properly.
Diamond sanding paper is only recommended for removal of very light oxide coatings on flat
surfaces such as analytical reference standards.
• Nickel, cobalt, and steel alloys should be ground using 36, 40, 50 or 60 grit discs.
The selection of a grit size of 100 or la
• inum, copper alloys, and other softer metals should be ground using 60 or 80 grit
discs.
• Grinding stones are not recommended because they will absorb surface material and
transfer them onto the next surface ground.
When using a grinder, follow these safety rules:
• When changing sanding discs, always remove the grinder battery to prevent
accidental activation of the grinder.
• Allow the grinder to stop spinning before placing it on a flat surface.
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