Developments of Novel Alloys for Bonding to Rubber

There have only been a very few attempts at research aimed at developing modified brass or alternative alloys for bonding to rubber compounds. After the failure of the ternary alloys of the type CuZnX (X = Co or Ni) around 1980, the focus of the tyre cord and rubber industries has been on the development of better compounds or tyre cord constructions. 

Only two developments are worth mentioning here. Giridhar developed a dual layer coating on steel wires consisting of a ZnCo base layer (1% Co) followed by a NiZn (30% Zn) top layer [27, 59-62]. Both alloys were deposited from simple acid sulphate baths. The advantages of this system are  

A drawback was that these cords were more difficult to draw than brass because the a-NiZn phase is harder than a-hrass. The a form is a crystalline, single phase state with up to 37% zinc present. 

The mechanism of adhesion of this cord has not been studied in great detail [27]. However, the limited work that was done indicated that the amount of the interfacial reaction products formed was considerably less than in the case of brass, and it cannot simply be assumed that Ni Sy would replace the function of Cu S. The corrosion resistance of this cord is much higher than of brass because Znl%Co has much better resistance than brass or even pure zinc. 

In a recent publication, the Pirelli group reported that the NiZn top layer had been dropped from the system and a new tyre had successfully been developed with the Znl%Co coating only [63]. By modifying the crystal orientation of the deposit and hy developing an optimised lubricant, a cord could be obtained with equal drawing behaviour. 

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