Ideally hydronic pipe should not be affected by the fluid it is carrying, and the fluid should not be affected by the pipe. Sadly, many HVAC system use a compromised material called carbon steel for hydronic piping. Water oxidizes steel, which causes pitting, scale build-up, and eventually leads to failure of the pipe. These effects are mitigated through the use of closed systems where possible, chemical treatment, PH-treatment, etc.
PTS Data Center Solutions, Inc. 