HOBAS Pipes do not conduct electricity and are not susceptible to attack caused by acids, alkalis and salts. There is a direct correlation between the resistance of HOBAS Pipes and the employed resin grade. Standard resins ensure that the systems are fit for today’s wastewater quality. This has a pH value of 1 to 10 and a maximum permanent temperature of 35°C. The standard grade (VA) is also resistant to the effects of biogenic sulfuric acid which occurs in large sewers with long retention times.
Special resins can be used to meet higher demands, such as in industrial applications (see resistance classes). Protective coatings or finishes are not required. Galvanic corrosion can be ruled out.
Strain Corrosion Test
A test used to determine how GRP pipes will react in the field is the strain corrosion test, which checks for stress corrosion cracking. Specimens are subjected to both physical (structural design) and chemical (medium) loading, i.e. the pipe is held in a deflected state in a sulfuric acid solution. The results of the standardized test according to ASTM 3681/3262 (American Society of Testing Materials) are conclusive because it is conducted on a pipe section on a scale of 1:1. It therefore reflects practical applications under more extreme conditions as closely as possible without requiring unnecessary tests for individual criteria that can also be contradictory in the case of composites. When this test procedure is conducted, HOBAS Pipes show a high level of fiber strain thanks to primarily the wall structure achieved with our production process. A glassfiber-free, at least 1 mm thick liner layer and a void free, highly compacted pipe wall ensure high resistance to diffusion. We have been performing these tests for a long time at the European plants, in the United States and Australia. Based on a service life of 50 years, HOBAS Pipes achieve a fiber strain level of at least ε=1.1%. As a result, HOBAS Pipes have high chemical safety margins when external loads are applied.