STUDIA UNIVERSITATIS BABEŞ-BOLYAI, CHEMIA, LV, 1, 37-44 Zn-Ni ALLOY COATINGS FROM ALKALINE BATH CONTAINING TRIETHANOLAMINE. INFLUENCE OF ADDITIVES. Liana Maria Muresan* 1 , Julien Eymard 2 , Diana Blejan 1 , Emil Indrea 3 1 “Babes-Bolyai” University, Department of Physical Chemistry, 11 Arany Janos St., 400028 Cluj-Napoca, ROMANIA.*E-mail: limur@chem.ubbcluj.ro 2 IUT Rouen, FRANCE 3 INCDTIM Cluj-Napoca, ROMANIA ABSTRACT. The Zn-Ni alloys have been electrodeposited from an alkaline bath containing triethanolamine as complexing agent for Ni 2+ ions. Polyethyleneglicol (PEG), coumarin, piperonal and vanillin have been tested as brightening agents. Their effect on the codeposition process and on the corrosion resistance of the resulted coatings was investigated. Under the examined conditions, the electrodeposition was of anomalous type. The effect of plating bath conditions on the corrosion resistance was studied by Tafel polarization measurements. It was found that the tested compounds had a beneficial effect both on deposits quality and on their corrosion resistance. Keywords: zinc - nickel alloys, electrodeposition, corrosion, triethanolamine 1. INTRODUCTION Zn-Ni alloys replace successfully cadmium coatings in the automotive industry [1] and provide superior sacrificial protection to steel than pure zinc since they corrode more slowly. Moreover, adhesion of chromate onto Zn-Ni alloy is superior to zinc. Zinc-nickel can be plated from acid [2-12] or alkaline noncyanide solutions [13-21]. Although Ni is nobler than Zn, the codeposition of Zn-Ni in both cases is anomalous and a higher percent of Zn is present in the final deposit [2]. The acid bath typically gives a higher Ni content than the alkaline one (i.e. 10-14% Ni vs. 6-9 %), with high current efficiency, but the distribution of the plated metal is poor. In contrast, alkaline electrodeposition is less efficient, but gives more uniform plating in both thickness of deposit and alloy composition [14]. Moreover, alkaline baths are non-corrosive. Basic alkaline baths usually contain Zn 2+ and Ni 2+ ions, an alkali metal hydroxide and a complexing agent for nickel, such as