Boiler make-up water and condensate can be very corrosive. Make-Up has oxygen. Higher level of make-up in a system introduce more oxygen. Higher levels of make-up require more steam for feedwater heat. If the water is heated in the tank by injecting steam through a sparge tube, there can be oxygen corrosion in the vessel. More steam and more oxygen result in faster corrosion in the vessel. If the condensate is acidic, which is normal, the condensate can increase the rate of corrosion further.
It is common for system with 70% or 80% make-up to wear out in 4 or 5 years due to oxygen corrosion. How can you guard against premature failure of the vessel? Use a corrosion resistant material or coating to protect against oxygen corrosion. Using a coating or stainless steel will extend the vessels life. The higher the level of make-up, the greater the need for a corrosion resistant lining. The severity of the expected corrosion may suggest on option over the other.