Heat Exchangers

• Galvanic corrosion at joints between dissimilar tube and shell metals (carbon steel water box, stainless tube sheet, copper-alloy tubes).
• Inlet-end tube erosion from high-velocity, particulate-laden cooling water.
• Water-box and end-cover wall loss from long-term immersion corrosion.
• Division-bar corrosion on multi-pass exchangers leading to internal pass-to-pass leakage.
• Flange-face damage on bolted heads, blocking gasket seating.
• External shell corrosion from insulation moisture and atmospheric exposure.

Why the water side fails first

The water box, end covers, and tube-sheet face see the worst combination of variables on a heat exchanger: dissimilar metals, electrolyte (cooling water), elevated velocity at the inlet, and limited drainability. Galvanic corrosion concentrates at the carbon-steel water box because it is the anode in the cell with the copper-alloy or stainless tubes. Rebuilding the metal loss is only half the job; the lining also has to break the electrical path that drove the corrosion.

Belzona product families used on heat exchangers

Metal-loss rebuilding on water-side surfaces

Belzona 1111 (Super Metal) is the standard composite for tube sheets, water boxes, end covers, division bars, and flange faces. Where the asset will return to immersion-temperature service, Belzona 1311 (Ceramic R-Metal) is selected for higher service temperature and erosion-corrosion resistance. Both cure cold, contain no solvent, and bond to manually prepared carbon steel.

Long-term protection topcoat

Belzona 1321 (Ceramic S-Metal) is rated for continuous immersion to 60°C (140°F) and is the standard topcoat over a 1111 or 1311 rebuild on cooling-water service. For higher-temperature immersion, Belzona 1391T extends the envelope and is the typical choice on hot-water and process-water exchangers. The polymer film also acts as the dielectric barrier that arrests the galvanic cell.

Tube inlet erosion

Inlet-end tube erosion on copper-alloy tubes is most often handled by sleeving or by tube-sheet face buildup; the polymer system protects the tube-sheet face and reduces turbulence at the tube entry. See the Heat Exchangers Tube Sheets page for the dedicated tube-sheet treatment.

Repair strategy on a planned outage

A typical exchanger overhaul scope reads: clean to NACE 2 / SSPC-SP10, hand-prepare per IFU, rebuild metal loss with 1111 or 1311, apply two coats of 1321 (or 1391T for hot service) at specified DFT, full cure at ambient, and reassemble. The crew can finish a 36-inch water box in a single shift and have the unit back on line inside the planned outage window.

Documentation and approvals

Belzona Baton Rouge supplies the per-product Product Specification Sheet (PSS), Instructions for Use (IFU), and SDS for each material on the exchanger. WRAS, NSF, and equivalent listings are tied to specific product codes (for example, Belzona 5811DW2 for potable-water duty). We confirm the relevant listing against your service file rather than asserting a blanket approval for the brand.