Assessing Adhesion Results - Failure Attributes

Many National and International Standards, including ISO 4624 & ASTM D4541, require the user to record not only the adhesion pull-off force but also the nature of the failure. This is done by examining the bottom of the dolly and assessing the failure. In ‘Advanced’ mode on the Elcometer 510 it is possible to select the 'Attributes' feature (Menu/Setup/Gauge Mode/Advanced) allowing the nature of the fracture to be recorded against each reading and stored within the batch.

 

Adhesion Testing Results

Examining The Dolly

a) Cohesive Failure: The coating fails within the body of a coating layer leaving the same coating on the surface and on the dolly face.

b) Adhesive Failure: Failure occurs at the interface between layers (intercoat) where one pulls away from the other. The “coating” on the dolly face will not be the same as that on the test area.

c) Glue Failure: When no coating is present on the dolly it must be recorded as a failure of the glue. This maybe due to incorrect or insufficient mixing of the component parts of the adhesive, incompatibility between the adhesive/coating/dolly/test surface.

 

Cohesive Adhesive Code
Cohesive Failure Layer1

Adhesive Failure Layers

Code

Description

 Code

Description

A

Substrate

 A/B

Substrate & Layer 1

B

Layer 1

 B/C

Layer 1 & Layer 2

C

Layer 2

 C/D

Layer 2 & Layer 3

D

Layer 3

 D/E

Layer 3 & Layer 4

E

Layer 4

 E/F

Layer 4 & Layer 5

F

Layer 5

 F/Y

Layer 5 & Glue

Y Glue Y/Z

Glue & Dolly

     

 

Adhesion Test Results

The data is saved in the batch and can be viewed at any time displayed as 

##.## MPa2 N% A M% A/B, where;

##.## MPa2 = Pull Force in MPa or other measurement units (psi, Newtons or Nmm-2)

N% = Cohesive failure percentage3
A = Cohesive failure layer
M% = Adhesion failure percentage3
A/B = Intercoat adhesive failure layers

 

For more information on the Elcometer 510, click here.

     

 

1 The number of layers can be user defined for each batch via Batch/New Batch/Number of Layers. This will affect the number of layers available for selection during attribute recording. The maximum number of layers available is five, excluding the substrate and glue.

2 Or equivalent units.

3 To the nearest 10%, in line with International Standards.