What is Adhesion Test of Mirror? Purpose of Adhesion test? Explain in details step by step procedure to perform Adhesion test.

The adhesion test of a mirror is conducted to assess the strength and durability of the reflective coating on the mirror’s surface. This test determines how well the reflective coating adheres to the underlying glass or substrate. The purpose of the adhesion test is to ensure that the mirror’s reflective coating remains intact and does not peel off or degrade over time, ensuring long-term performance and stability.

Here is a step-by-step procedure to perform the adhesion test on a mirror:

1. Preparation:
   • Ensure that the mirror surface is clean and free from any contaminants. Clean the mirror using a mild cleaning solution and a lint-free cloth.
   • Allow the mirror to dry completely before proceeding with the adhesion test.
2. Selection of Test Method:
   • There are various methods available to perform the adhesion test, including tape tests, cross-cut tests, and pull-off tests. Select the appropriate method based on the specific requirements and industry standards.
3. Tape Test Method:
   • This method involves using adhesive tape to evaluate the adhesion strength of the mirror’s coating.
   a. Tape Selection: Choose a suitable adhesive tape that adheres well to the mirror’s coating. Commonly used tapes include pressure-sensitive tapes or duct tapes.b. Tape Application: Apply the tape firmly to the mirror’s surface, ensuring complete contact with the reflective coating. Press the tape uniformly to ensure good adhesion.c. Tape Removal: After the tape is applied, swiftly and firmly peel off the tape in a single motion, perpendicular to the mirror surface. The tape should be pulled off at a 180-degree angle.d. Examination: Inspect the tape and the mirror surface after tape removal. Evaluate the appearance of the tape and the mirror coating for any signs of coating removal, delamination, or peeling.e. Adhesion Rating: Assign an adhesion rating based on industry standards or specifications. This rating assesses the extent of coating removal or damage observed on the tape and mirror surface.
4. Cross-Cut Method:
   • The cross-cut test involves creating a grid of shallow cuts on the mirror’s surface to evaluate the adhesion of the coating.
   a. Grid Preparation: Use a cutting tool, such as a sharp blade or a specialized cross-cut tool, to create a series of cuts in the mirror’s coating. Make perpendicular cuts to form a grid pattern, creating small squares or rectangles.b. Tape Application: Apply adhesive tape over the cuts, ensuring complete contact with the mirror surface.c. Tape Removal: Firmly and swiftly peel off the tape from the mirror’s surface, following a 180-degree angle.d. Examination: Inspect the tape and the mirror surface for any coating fragments or chips adhered to the tape. Evaluate the number and size of coating fragments, which indicate the adhesion strength.e. Adhesion Rating: Assign an adhesion rating based on the industry standards or specifications, considering the size and number of coating fragments observed on the tape.
5. Pull-Off Method:
   • The pull-off test involves using specialized equipment to measure the force required to detach the coating from the mirror’s surface.
   a. Equipment Setup: Set up a pull-off tester according to the manufacturer’s instructions. The equipment typically includes a loading device and a calibrated measurement system.b. Attachment: Attach a specialized pulling device to the mirror’s coating, ensuring a secure grip.c. Force Application: Apply a gradually increasing force using the pull-off tester until the coating detaches from the mirror surface.d. Measurement: Measure and record the force required to remove the coating. Compare the measured force with the specified adhesion strength requirements.e. Adhesion Rating: Assign an adhesion rating based on industry standards or specifications, considering the measured force value.
6. Evaluation:
   • Compare the observed results with the specified adhesion requirements for the mirror’s intended application.
   • Determine whether the mirror’s coating has sufficient adhesion strength or if further actions, such as rework or rejection, are necessary.

It’s important to follow established industry standards and guidelines for performing the adhesion test and interpreting the results. Adhesion testing helps ensure that the mirror’s reflective coating adheres effectively to the substrate, preventing coating failure, degradation, or peeling, and ensuring long-lasting optical performance.