Polishing Cloths (PSA)

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Polishing is the most important step in preparing a specimen for microstructural analysis. It is the step which is required to completely eliminate previous damage. Ideally the amount of damage produced during cutting and grinding was minimized through proper blade and abrasive grinding so that polishing can be minimized.

Polishing Cloths
Cloths for polishing vary by the height of their fiber, known as the nap and by the stiffness or resiliency of the fiber. In general, the lower nap (also non-woven) and stiffer fiber cloths are used for the rough polishing steps. These types of polishing cloths or pads are very effective in removing sectioning damage done by cutting and coarse grinding. Conversely, higher napped polishing cloths provide a more gentle abrasive interaction for the final polish. The polishing pads are available with either a pressure sensitive adhesive (PSA) or on a magnetic backing. The following is a list of most common polishing cloths:

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POLISHING CLOTH SELECTION GUIDELINE

	Metal Mesh cloth - this is a wire mesh material useful for coarse and intermediate lapping/polishing. The texture of this wire allows for the abrasive to become semi-fixed; thus offering the advantage of increased stock removal, while minimizing damage
	POLYPAD Polishing Pad - this cloth is a synthetic polyester polishing pad which has a similar action to a nylon pad, with the exception that it is much more durable. It is used in the intermediate polishing steps
	TEXPAN Polishing Pad - this is the most commonly used polishing cloth material for the intermediate polishing steps. TEXPAN Polishing pad is a non-woven polishing pad.
	DACRON Polishing Cloth - this is a low napped polishing pad for polishing primarily with 1-15 micron diamond abrasives. The DACRON pad is the most popular intermediate polishing pad in Europe and is used mostly for polishing metals. Its high nap provides it a very soft and gentle polishing action. Note: DACRON is a registered trade name of DUPONT Corporation.
	GOLDPAD Polishing Pad - this is a low napped nylon polishing pad for polishing primarily with 1-9 micron diamond abrasives. It is very similar to the DACRON pad, however it has a thinner backing and thus provides better flatness and edge retention. Note: DACRON is a registered trade name of DUPONT Corporation.
	ALTANTIS Polishing Pad - is a low napped nylon polishing pad with a very soft backing. It is for polishing primarily with fine polycrystalline diamond abrasives (0.10, 0.25, 0.5, 1, 3, and 6 micron). The ATLANTIS polishing pad provides a excellent surface finish and is used mostly for polishing metals where edge retention is not as important as surface finish (e.g. welds and grain size analysis).
	Black CHEM 2 Polishing Pad - this is a porometric polymer pad which has a consistency similar to a rubber type of pad. Black CHEM pad has a low nap but behaves as an intemediate polishing pad with a performance between low napped and high napped pads.
	MICROPAD Polishing Cloth - this is the most common high napped final polishing pad for most metals and polymers. Its high nap provides it a very soft and gentle polishing action.
	NAPPAD Polishing Pad - this is another high napped final polishing pad useful for most metals and polymers. It has a higher nap than MICROPAD, providing it with a very gentle polishing action which is very useful for polishing soft materials such as copper, aluminum and austentite steels.
	MOLTEC 2 Polishing Pad - this is a wool polishing cloth used for final polishing and has a very high nap. It is most commonly used for final polishing metals where edge retention is a minimal consideration.

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RECOMMENDED PROCEDURES (Polishing Pads)

• Place pad on a flat lap plate
• Pre-charge pad with abrasive suspension, paste or powder
• Apply necessary lubricant
• Begin polishing with lower force to avoid tearing pad
• Clean specimen and pad for final 10-15 seconds of polishing cycle
• Clean and dry specimens

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POLISHING PROCESS DESCRIPTION

Polishing can be broken into two stages: rough and final polishing. Proper rough polishing removes all subsurface damage produced during cutting and grinding. In most cases this is accomplished with polycrystalline diamond abrasives and low napped polishing cloths. The final polishing step should be kept to a minimum and used only to clean up surface blemishes. Note that excessive final polishing times can result in phase relief, edge rounding, smeared material and inclusion pull-out. Final polishing is accomplished with high napped cloths and fine graded alumina or colloidal silica abrasives.

Minimizing Polishing Artifacts

To minimize polishing artifacts such as edge rounding, phase relief, smeared metal, grain pull-out and inclusion pull-out, the polishing time needs to be kept to a minimum. This can be accomplished by:

• minimizing sectioning damage
• grinding with the finest feasible abrasives
• using flat polishing base plates

Minimizing sectioning damage and using the correct grinding abrasives are fairly obvious. However, using a flat supporting plate is generally over looked by most suppliers of metallographic equipment, and if they do consider plate flatness they generally do not go far enough. As a guideline, an 8-inch plate should have no more than a 0.0001 inch (2.5 um) runout, which represents a 0.6 um runout over a 1-inch diameter specimen. Recognize that final polishing abrasives have a typical size of 0.05-0.06 um, thus these tolerances are required to minimize polishing times. In addition, if the specimen is not flat on the polishing plate then a differential pressure occurs across the specimen, which causes polishing relief. Likewise for a 12-inch diameter plate the runout should not exceed 0.0002 inches (5 um). As a result both polishing times and differential polishing pressures can be minimized.

Suggestion: If your polishing plate is not flat within these tolerances they should be lapped to these tighter tolerances.

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TROUBLE SHOOTING for POLISHING

Symptom	Cause	Action
Coarse scratching	Contamination on polishing pad	Replace with a new pad
Tearing of pad	Too high a polishing force Improper lubrication	Reduce polishing force Dispense lubricant or abrasive more frequently
Excessive relief or edge rounding	Improper polishing pad selection Excessive polishing times	Refer to polishing cloth guide Reduce polishing times and re-examine effectiveness of previous step

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POLISHING PRODUCT DESCRIPTION (PSA)
(For Magnetic click here)

METAL MESH ABRASIVE CLOTH (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
CERMESH metal mesh cloth	8	5/pkg.	CMESH-2008
CERMESH metal mesh cloth	10	5/pkg.	CMESH-2010
CERMESH metal mesh cloth	12	5/pkg.	CMESH-2012

POLYPAD POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
POLYPAD polishing pad w/ PSA	8	10/pkg.	PP-6008
POLYPAD polishing pad w/ PSA	10	10/pkg.	PP-6010
POLYPAD polishing pad w/ PSA	12	10/pkg.	PP-6012

Black CHEM 2 POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
Black CHEM 2 polishing pad w/PSA	8	10/pkg.	BC-8008
Black CHEM 2 polishing pad w/PSA	10	10/pkg.	BC-8010
Black CHEM 2 polishing pad w/PSA	12	10/pkg.	BC-8012

DACRON POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
DACRON polishing pad w/ PSA	8	5/pkg	DC-3008
DACRON polishing pad w/ PSA	10	5/pkg	DC-3010
DACRON polishing pad w/ PSA	12	5/pkg	DC-3012

Note: DACRON is a registered tradename of Dupont Corporation.

TEXPAN POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
TEXPAN polishing pad w/ PSA	8	10/pkg.	TP-5008
TEXPAN polishing pad w/ PSA	10	10/pkg.	TP-5010
TEXPAN polishing pad w/ PSA	12	10/pkg.	TP-5012

MICROPAD POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
MICROPAD polishing pad w/PSA	8	10/pkg.	MP-9008
MICROPAD polishing pad w/PSA	10	10/pkg.	MP-9010
MICROPAD polishing pad w/PSA	12	10/pkg.	MP-9012

NAPPAD POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
NAPPAD polishing pad w/ PSA	8	10/pkg.	NP-7008
NAPPAD polishing pad w/ PSA	10	10/pkg	NP-7010
NAPPAD polishing pad w/ PSA	12	10/pkg	NP-7012

MOLTEC POLISHING PADS (w/ PSA)
Description	Diameter (inches)	Quantity	Catalog Number
MOLTEC polishing pad w/ PSA	8	5/pkg	MT-7008
MOLTEC polishing pad w/ PSA	10	5/pkg	MT-7010
MOLTEC polishing pad w/ PSA	12	5/pkg	MT-7012

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MAGNETIC POLISHING BASE for PSA backed POLISHING PADS
Description	Diameter (inches)	Quantity	Catalog Number
8" magnetic base plate (PSA backed)	8	each	MAG-B08
10" magnetic base plate (PSA backed)	10	each	MAG-B10
12" magnetic base plate (PSA backed)	12	each	MAG-B12
8" teflon coated base plate	8	each	MAG-P08
10" teflon coated base plate	10	each	MAG-P10
12" teflon coated base plate	12	each	MAG-P12