Various types of polymeric materials are usually subjected to different types of mechanical or physical damages during manufacturing process, shipping, handling, installation or service. Such damages will affect protective coatings’ integrity. Once the barrier properties of the coatings are compromised, water, chemicals, and electrolytes can reach the underlying metal substrate which can lead to further crack propagation, delamination, and blistering of the coating as well as corrosion of the substrate. Impact resistance indicates the ability of a coating to resist cracking or breaking caused by impacts, which is one of the most critical mechanical properties to be considered in order to ensure a protective coating keeping its role in proper perspective.
The falling-weight impact test, also known as the drop impact test, is one the most widely used methods for determining the impact resistance. The test employs a falling fixed weight having a specified diameter impact surface, tup, which is restrained vertically and dropped from varying heights to produce impact energies. The kinetic energy possessed by the falling weight at the instant of impact equals to the energy used to raise the weight to the height of the drop and is the potential energy possessed by the weight as it is released. Based on this, the impact energy is calculated by multiplying the impact weight and the drop height and the units are usually expressed in inch pounds, kilogram meters or joules. This test method can be used to determine the amount of energy required to cause penetration of a coating film under specified conditions of impact, to predict the performance of a coating for its ability to resist cracking by impact, or to provide a systematic means for screening coating materials with regard to this property.
Test methods for the impact resistance are available in:
- ASTM G14
- ASTM D2794
- CSA Z245.20 Section 12.12
- NACE SP0394 Appendix I
- ISO 21809-1 Annex E
- ISO 21809-2 Annex A.14
- ISO 21809-3 Annex D
- BS EN 10289 Annex C
- BS EN 10290 Annex C
- BS EN 12068 Annex H
- DIN 30670 Annex H
Test Samples:
Coated steel panels or external coated pipes