Abstract
For more than 50 years, the industry has been using coatings and linings for the protection of steel tanks used for the storage, transport, or processing of chemicals. Sometimes, the linings protect the chemicals from contamination by steel or rust or are used for easier cleaning of the tank walls. In all cases, the lining has to adhere firmly to the substrate without film defects such as blistering, peeling or cracking which would interfere with their function.
During those 50 years, new resins, pigments, and additives, as well as surface preparation and application techniques, have been developed to improve the performance and the economics of tank linings. But, simultaneously, environmental and safety regulations have changed. Safety (OSHA) and Environmental Regulations (VOC, HAP) forced the coating industry to develop compositions even when this was not always congruent with the performance requirements. New testing techniques had to be developed and implemented in order to predict more accurately the field performance of the coatings.
Undoubtedly, the trend is towards very high solids or preferably solvent-free coatings. The use of water as a viscosity-reducing liquid in emulsion coatings would still be acceptable under certain conditions. But where higher molecular weight resins could very well be used in solvent-containing coatings, those resins would present viscosity problems in solvent-free coatings. Using low viscosity “reactive” or “non-reactive” diluents can solve the viscosity problem but can easily lead to reduced chemical and mechanical properties.
This paper will present work that has been done to eliminate many of the problems described, including the risk of “off-ratio” mixtures due to the malfunctioning of plural component spray equipment or human errors.
