IFAN Customized Brass Press Fittings

The galvanic series predicts corrosion risk
Different metals have different electrochemical potentials. Brass is more noble (cathodic) than galvanized steel. Stainless steel is even more noble than brass. Brass press fittings create a galvanic cell when joined to dissimilar metals .

Three conditions must be present
Galvanic corrosion needs three specific conditions. First, two dissimilar metals must touch electrically. Second, an electrolyte (like water) must connect them. Third, a closed circuit completes the path. Brass press fittings meet all three when installed .

Brass against galvanized steel
Galvanized steel is coated with zinc. Zinc is anodic to brass by a large margin. The potential difference is about 750 mV . Brass press fittings will cause the zinc coating to corrode rapidly. The steel underneath then rusts quickly .

Example: a water heater connection
A galvanized steel pipe connects to a brass press fitting. Water acts as the electrolyte. The zinc coating dissolves within months. Brass press fittings survive, but the steel pipe fails. Example: the pipe wall thins until it leaks.

Brass against stainless steel
Stainless steel is very close to brass in the galvanic series. Admiralty brass ranges from -0.28 to -0.36 volts. Stainless steel (passive) is around -0.08 to +0.08 volts . Brass press fittings paired with stainless have low risk.

The passive layer matters
Stainless steel's corrosion resistance comes from a passive oxide layer. This layer can fail in low-oxygen environments. When active, stainless steel becomes anodic to brass. Brass press fittings may then corrode instead .

Example: a buried stainless steel pipe
A stainless steel pipe connects to a brass press fitting underground. Soil lacks oxygen for passive layer maintenance. The stainless becomes active and anodic. Brass press fittings corrode in this scenario. Example: the brass fitting pinholes within two years.

The cathode-to-anode area effect
A small anode connected to a large cathode corrodes very fast. If a brass fitting (cathode) connects to a long galvanized pipe (anode), damage concentrates. Brass press fittings being small cathodes can destroy large anodic areas. Example: a 1-inch brass tee on 50 feet of galvanized pipe accelerates corrosion .

O-ring selection influences risk
EPDM O-rings seal water systems effectively. HNBR O-rings seal hydrocarbon systems. Brass press fittings use both seal types depending on application . The O-ring material does not prevent galvanic issues directly.

Dielectric isolation as a solution
A dielectric union separates dissimilar metals electrically. Plastic sleeves or gaskets break the conductive path. Brass press fittings can be isolated from steel pipes this way. Example: a dielectric nipple with a plastic liner between brass and galvanized pipe .

Industry standard solutions exist
Merit Brass offers CarbonPress fittings for steel pipe systems. These are carbon steel with Zn-Ni plating, not brass. Brass press fittings made of carbon steel eliminate the galvanic mismatch entirely . Use matching materials for long-term reliability.

Final compatibility summary
Brass press fittings have low galvanic risk with stainless steel. The potential difference is small, especially in oxygenated water. With galvanized steel, the risk is very high. The zinc coating corrodes rapidly when connected to brass. Use dielectric unions or matching material fittings. Never directly connect brass press fittings to galvanized steel pipes. For stainless steel, verify the environment maintains passivity. When in doubt, choose fittings of the same material as your pipe. Example: stainless steel fittings for stainless steel pipes prevent all galvanic concerns .

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