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Given your makeup water chemistry and the goal to run at 2 cycles of concentration, silicates are not the best primary corrosion inhibitor choice for this system. The alkalinity and calcium are too high, and silicates won’t protect against all corrosion threats. A PBTC + zinc + dispersant program is better suited to your water, system metallurgy, and performance goals.

Cloud HQ ( Ashburn ) System Chemistry at 2 Cycles (Estimated):

These values indicate moderately hard, moderately alkaline water. You’re operating in conditions where:

• Scaling (especially calcium carbonate) could occur
• Corrosion is also a concern due to relatively low cycles (higher % of fresh water, more aggressive)

• Why Silicates Aren’t Ideal Here:
  1. Alkalinity is Too High for Silicates Alone
  2. At >200 ppm M-alkalinity, silicates may not form a stable film
• High alkalinity + calcium = risk of calcium silicate scaling if silica levels climb
• pH May Drift Too High
  8. With natural cycling, the pH could rise to >8.4, increasing:
     1. Risk of silicate precipitation
     2. Iron corrosion, especially in turbulent or oxygen-rich areas

• Not Broad-Spectrum
  1. Silicates primarily protect mild steel, but don’t address:
     1. Copper corrosion
     2. Scale control unless paired with dispersants

• Microbial activity (they don’t suppress biofilm or algae)

• Better Treatment Strategy for Your Water:
  1. A low-phosphate, zinc-stabilized program with PBTC and polyacrylate dispersants would likely be more effective and reliable, such as:
• Suggested Approach:
  1. PBTC (2–5 ppm active): Chelates metals, controls scale, helps stabilize zinc
  2. Zinc (0.5–1.5 ppm): Cathodic corrosion inhibitor for steel
  3. Polyacrylate (5–10 ppm): Dispersant for calcium, iron, and magnesium
  4. Azole (e.g., tolyltriazole or BBT): If copper/brass are present
• This approach offers:
  1. Strong corrosion protection for steel and copper
  2. Better stability at higher pH and alkalinity
  3. Improved biofouling and scale control support