Table 26 Applications of Brasses in Aggressive Environments

The information in this brief summary of some of the recommendations made for the uses made of brasses in contact with chemicals, building materials, etc., is largely taken from E Rabald’s (, Corrosion Guide.

All copper alloys are rapidly attacked by ammonia in moist conditions, with the formation of a bright blue corrosion product, and contact should therefore obviously be avoided. Even in very low concentrations of ammonia, brass that is stressed by either residual or applied tension will spontaneously crack by 'stress corrosion', a phenomenon first observed many years ago and at that time called 'season cracking'. For failure to occur in this way, two conditions must apply: that the brass is under stress, and that ammonia is present (Mercury and moist chlorine may also cause similar failure). Internal tensile stresses caused by cold working, as in the cold drawing of tubes or cold bending of pipework, are sufficient to make brass susceptible to stress-corrosion cracking. Under such circumstances a stress-relief heat treatment is advisable before such items are put to use in aggressive environments. Test methods to ensure that the heat treatment has been effective are detailed in relevant British Standards, BS2871, Parts 2 and 3 and BS2874; also in BS EN ISO 196 and ISO 6957.

Dry chlorine and very low concentrations of chlorine in solution, such as the dosing of seawater to prevent marine fouling, and biocidal additions made to swimming pool water, present no difficulties and no corrosion problems are encountered when brass components are used. Brass is completely unaffected by the full range of medical gases; likewise gaseous fuels, with the exception of acetylene, do not affect brass.

The duplex 60/40 alloys are satisfactorily used for the manufacture of acetylene control valves for welding and cutting equipment. However the single phase alpha brasses containing over 64% of copper should not be used in contact with acetylene due to the likelihood of the formation of explosive copper acetylide.

Seawater can cause dezincification to occur in duplex brasses, but in heavy sections such as condenser and heat exchanger tube plates and propellers, the rate is low enough for them to give a good economic life. The single phase brasses, with an inhibiting arsenic addition, are widely used for tubing seawater cooled heat exchangers and condensers, and for the construction of seawater pipework for shipboard installations, in which applications they give excellent service. Dezincification resistant brasses are also approved for through-hull yacht fittings.

The brasses are resistant to alkalis, organic acids, the full range of industrial solvents and refrigerants. However, brasses are not suitable for use in contact with ammonia or strong mineral acids such as nitric or hydrochloric. Foodstuffs do not corrode brasses significantly, but prolonged contact may cause a sufficient amount of copper pickup to occur to give the food an unpleasant, though non-toxic "metallic" flavour. For this reason, it is normal practice to coat brass parts with either tin, nickel or chromium when they are to be used in contact with foodstuffs.

Lubricating oils, transformer oil, fuels and hydraulic fluids do not attack brass significantly. Copper pickup can accelerate the oxidation and consequent "sludging" of some of these substances but normally commercial products contain anti-oxidants to prevent such problems arising. The biocidal nature of copper means that water-based lubricants do not become a health hazard due to the growth of micro-organisms.

Detergents and most cleaners in domestic use, are quite compatible with brass and cause no problems. A few powerful domestic cleaners do however contain ammonia and while normal contact with these substances does not result in any noticeable attack, prolonged exposure, such as overnight soaking should be avoided.

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