Adhesion Test of Paint & Coating: Definition, Testing Methods, Purpose and Standard Specifications

What Is an Adhesion Test:-

Adhesion test is used to evaluate the bonding strength of coating with substrate by checking paint removal after applying mechanical stress with adhesive tape.

An adhesion test is a quality control test used to determine how strongly a paint or coating is bonded to the substrate (metal surface).

In simple terms, the adhesion test confirms whether surface preparation, coating application, and curing have been carried out correctly.

Testing Methods of Adhesion Test:-

1. Tape Test (Cross-Hatch Method) – Most Common

This is the most widely used adhesion test, especially for CED, liquid paint, and powder coating.

Procedure:-

Cross-hatch cuts are made on the coated surface .
A pressure-sensitive tape is applied over the cuts.
The Adhesive tape is removed at a 180° angle.
The amount of paint removal is visually evaluated.

2. X-Cut Tape Test-

An “X” shaped cut is made on the coating.
Tape is applied and removed.
Commonly used for field inspection or vendor audits.

3. Pull-Off Adhesion Test-

Performed mainly in laboratories.
A vertical pulling force is applied to the coating Approx 2Kg.
Adhesion strength is measured in N/mm².

Specification of Adhesion Test as per Standards:-

ASTM D3359 – Cross-Hatch Tape Test

Number of cuts: 6 × 6 (25 squares)
Cut spacing:-
DFT ≤ 50 µm → 1 mm
DFT > 50 µm → 2 mm
DFT > 150 µm → use X - Cut Method
Acceptance criteria:-
5B: No coating removal (Excellent)
4B: Very small coating removal at edges (Acceptable)

ISO 2409 – Coating Adhesion Test Standard

ISO Class	Description	Result
Class 0	No flaking	Pass
Class 1	Very small flaking	Pass
Class 2	Slight flaking	Conditional
Class 3–5	Significant flaking	Reject

Very small flaking” means:-

Minor coating removal only at the edges of the cuts
No complete square removal
Total affected area is less than 5%

Purpose of Checking Adhesion Test:-

The main purposes of performing an adhesion test are:

To evaluate the bonding strength between coating and substrate
To verify the effectiveness of degreasing and phosphating processes and Also Curing Process.
To ensure CED coating quality and durability
To prevent future defects such as peeling, flaking, or blistering
To meet customer specification requirements

~Thanks for Reading This Blog~

Adhesion Test of Paint & Coating: Definition, Testing Methods, Purpose and Standard Specifications

What Is an Adhesion Test:-

Testing Methods of Adhesion Test:-