Metallic Sample Preparation
For repeatable measurements results, identical surface preparation of samples before conducting tribocorrosion tests can be essential to ensure reliable results.
Coupon size
Coupons must have a defined size for being able to be fixed on the sample holder. Square and rectangular samples are easier for sample fixation. It is possible to cut metallic alloys into several coupons, larger than 1.5 × 2 cm2 in dimensions. The objective is to have a space available of 1 x 1 cm2. For corrosion rate, the exposed area must be known. An area of 1x1 cm2
is fine.
is fine.
Recommended Procedure for Sample Surface Preparation prior to Tribocorrosion Testing
Mechanical Grinding
- Grind one side of the sample surface using sandpaper with progressively finer grit sizes (#180, #240, #400, #600, and #1200).
- Begin with #180 sandpaper, grinding for 30 seconds along an arbitrary direction.
- Rotate the sample 90° and grind with #240 sandpaper until all scratch lines from the previous step are fully removed.
- Verify the surface using an optical microscope to ensure complete elimination of
scratches.
- Repeat the rotation and grinding sequence with the remaining grit papers, cleaning the sample between each step using a soft brush under running water to prevent contamination.
Polishing
- Polish the ground surface sequentially using high-viscosity alumina suspensions with particle sizes of 1 μm, 0.3 μm, and 0.05 μm, applied on separate microfiber cloth pads.
- For each polishing stage, pour approximately 1 oz of alumina suspension (composition: 10–30% alumina, 0.6–1% silica glass, 70–90% water) onto a clean pad.
- Polish the surface in a single direction or in a “figure-eight” motion (avoid circular “0” motions) until scratches from the previous step are no longer visible.
- Continue through finer suspensions until achieving a mirror-like finish.
Cleaning
- Place the polished specimen in a beaker containing 40 mL of deionized (DI) water and sonicate for 1–2 minutes to remove residual surface particles.
- Dry the surface completely using compressed gas.
Electrical Connection
- Cut a 5 cm length of electrical wire (~1–2 mm diameter) and strip approximately 1 cm of insulation from both ends to expose the copper core.
- Attach one end of the wire to the unpolished back side of the sample using conductive tape or conductive epoxy. If epoxy is used, follow the manufacturer’s curing instructions.
Masking
- Apply electrochemical stop-off lacquer to define a 1 × 1 cm2 exposed window on the polished side of the sample and to cover the entire back side, including the area with the attached wire.
- Allow the lacquer to dry completely in a well-ventilated fume hood for at least 24 hours before conducting the experiments.
Made with Bullet