CORRODERE
A brief guide to adhesion testing
Good adhesion is critical to the integrity and long-term performance of a coating . Poor adhesion can result in failure , corrosion and contamination of surfaces or contents . So , it ’ s vitally important to undertake adhesion testing to assess the quality of the attachment between the dry paint film ( coating ) and its substrate .
How can this be achieved quickly and effectively ? There are several ways , but it ’ s important to agree on the method , standard and quantity of any tests with the client or owner in advance of any work starting .
Firstly , ensure effective coatings training has been undertaken . Secondly , test adhesive integrity using two basic methods .
Use a knife to cut through the coating down the substrate in the shape of an X or several parallel cross cuts . It offers an indication of a potential adhesion issue , which may warrant further investigation . There are several ISO and ASTM standards to be observed using this method including ISO 16276-1 , ISO 16276-2 , ASTM D6677 ( evaluating adhesion by knife ) and ASTM D3359 ( rating adhesion by tape test ), ISO 4624-Paints and varnishes and ASTM D7234 ( pull-off adhesion strength of coatings on concrete portable pull-off adhesion testers ).
Another other approach is to cement an aluminium dolly onto the coating . This type of method is most effectively instigated by those who have undertaken a coatings survey course . An adhesion test apparatus pulls away and is used to evaluate the tensile strength of the coating . A numerical value in pounds per square inch ( psi ) or Mega Pascals provides adhesion strength readings . This quantitative approach to testing will identify a failure along the weakest plane ( S ) within the costing system and can identify glue failure or intercoat failure . It ’ s important to note that the use of the pull-off gauge and description of the mode ( s ) of failure can give inconsistent results .
It is important to note that a trained Coating Surveys specialist should conduct this test – the process can produce variable results or a different interpretation of results , so an expert view is critical . In conclusion , the mode ( s ) of failure depending upon whether the surface has been abraded , the shape and size of dolly , coating thickness , age , and hardness , and the degree of cure of the coating among several factors .
The online Coating Surveys course from Corrodere Academy is a world-first – there is no other coatings training like this , available anywhere in the world . It is specifically written for individuals working in the coatings industry . Accredited by Lloyd ’ s Register , SSPC and the Institute of Corrosion - this coatings course aims to drive consistency throughout the coating industry and ensure more accurate forecasting of maintenance works and investment . It will assist with paint guarantees , warranties , disputes and more . Plus , you also get a free copy of the Fitz ’ s Atlas of Coating Surveys when you sign up to the course .
To find out more and ensure consistent high standards throughout coating testing projects , contact the team at Corrodere today .
Telephone : + 44 ( 0 ) 1252 732 236 Email : info @ corrodere . com Visit : www . corrodere . com
8 JUNE 2021 read online : www . surfaceworld . com