Problem Solving Forum
April 17 - April 23, 2016
What are the differences between calcium sulfonate modified alkyd (CSA) and high-ratio calcium sulfonate alkyd (HRCSA) in terms of performance and when and where each is used?
Wayne Senick of Termarust Technologies on
April 26, 2016:
The difference between an HRCSA High Ratio Co- pol ...read more The difference between an HRCSA High Ratio Co- polymerized Calcium Sulfonate and a CSA Calcium Sulfonate- modified alkyd is quite substantial. The HRCSA High Ratio Co-Polymerized Calcium Sulfonate Primer/Topcoat is a pigmented type of co-polymerized, reacted synthetic resin with a unique patented crystalline modification that cures by air oxidation. HRCSA coatings are formed by reacting a specific acid, using a proprietary process, and a base made of a specific synthetic (grown artificially as opposed to natural crystalline) base material with polymers, to form an active chemistry for the control of corrosion, crevice corrosion and pack rust.This formula was developed in the mid-1980's and was first installed on a structure in 1990. Since then, the formulation has remained unchanged and been installed on thousands of structures worldwide. A unique feature of the HRCSA system is the active penetrant sealer used to stop crevice corrosion and pack rust in joints and free up corrosion-frozen bearings. An HRCSA coating can be generically specified and identified by its chemical properties. A HRCSA primer/topcoat will contain a minimum 9.5% active sulfonate, must maintain a 9-11 to 1 ± 2% ratio total base number to active sulfonate, i.e., total base number of 85 to 104 to 9.5% active sulfonate as determined by titration testing. The HRCSA penetrant /sealer will have a minimum 15% active sulfonate, must maintain a 9-11 to 1 ± 2% ratio total base number to ctive sulfonate, i.e., total base number of 135 to 165 to 15% active sulfonate as determined by titration testing. The HRCSA coatings are chemically active, high-performance, single-coat, single-component, environmentally friendly coatings that, when tested by independent government laboratories, consistently out- performed both high performance barrier and sacrificial barrier coating systems.The FHWA lab in Mclean VA tested the HRCSA against standard systems, and the HRCSA after ASTM B5894 with a 24-hour, -40 C freeze-thaw went 6840 hours (19 cycles) with no undercutting at the scribe. CSA coatings, on the other hand, are calcium sulfonate-modified alkyd coatings and resulted from a generic specification that was developed around a total weight of 15% calcium sulfonate-calcium carbonate resin. This type of generic is open to interpretation by manufacturers. Depending on the desired performance or price point the manufacturer wants to achieve, the amount of active sulfonate can vary from .5% to 5.5%, and the total base number can range up to 300+ usually made up of calcium carbonate filler. The performance of these materials varies from 300 to 1500 hours ASTM B5894. CSA coating are typically used as short-term maintenance coatings with a maximum performance service life of 5 years. The two major points of difference between the two systems are the formulations and the performance. HRCSA is one formulation that has not changed in 30 years and can be verified. The HRCSA coatings are a high-performance long-term rust- mitigation system with a 26-year field proven history. CSA coatings are a function of the manufacturer's interpretation of the 15% by weight specification and the performance is as variable as the interpretation of the specification.