Development of Hybrid Electro-Electroless Deposit (HEED) Coatings and Applications

Abstract

Since the discovery of electroless deposition within the electroplating process, the two techniques have grown as two separate, yet parallel, means of deposition. This paper demonstrates the reunification of the two processes in what is herein named hybrid electroelectroless deposition, or HEED. Specifically, the novel reunification as outlined within this study demonstrates that electroplating and electroless deposition can be achieved from a single solution wherein each process specifically targets a different metal ion within the electrolyte. The successful production of a compositionally modulated Au/Co/Au tri-layer from a single electrolyte using modulated electroless and electro-plating is described. Additionally, the practical application of producing compositionally modulated Ni-Zn-P alloy layers on AZ91D Mg alloys is demonstrated. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0331410jes] All rights reserved. Modern applications of electro-and electroless plating, in both industry and academia, have kept the two deposition techniques as largely two separate processes. The advantages and disadvantages of both processes are well known and documented 1 with each process having complimentary attributes with respect to the other. Examples of the complimentary nature of the processes include the ability to easily coat recessed areas with electroless deposition as well as deposit pure metal, along with alloys, using electroplating. Combining electroless deposition with electroplating in a novel process we have termed hybrid electro-electroless deposition (HEED) a provides benefits from both processes and allows for the formation of many unique thin film coatings using aqueous electrolytes.Hybrid electro-electroless deposition (HEED), as defined in our work, is the targeted reduction of different metals, or alloys, by each of the plating techniques from a single electrolyte. As a matter of definition the process requires the reduction of the 'primary' metal/alloy by means of electroless deposition while a 'secondary' metal/alloy can also be electroplated at a later stage from the same electrolyte. The selection of the term 'primary' for the electrolessly deposited metal is due the electrolessly deposited metal/alloy having typically a higher nobility than the secondary electroplated metal, as well as the requirement that electroless deposition must remain uninhibited by the presence of the secondary metal. That is to say the secondary metal must not impede or prevent the occurrence of electroless deposition. The union of electroless deposition with electroplating using HEED allows for the deposition of multi-layered structures as well as the deposit of well controlled alloys and composites.Traditional methods of depositing both alloys as well as compositionally modulated multi-layers, including dual bath systems and electroplating alone, offer deposits of increased hardness 2 as well as enhanced corrosion 3-6 and wear resistance. 7,8 Additionally, multilayer deposits are known to possess beneficial and pra...

Deposition of Cobalt-Nickel Hybrid Electro-Electroless Deposited (HEED) Modulated Multilayers

“…1 Electroplating was chosen to form the first layer as a matter of convenience, as only a conductive surface was required and no pretreatment of the Cu substrate was necessary. The conditions for the formation of each layer, Table III, and specifically the electroplating potentials, were slightly different for each layer due to the system as well as changes in the electrolyte.…”

“…Co(Ni-P)/Ni-P pentalayer.-Both electroplating and electroless deposition for the Co(Ni-P)/Ni-P pentalayer was carried out within the electroplating cell as described in the initial presentation of HEED coatings. 1 Electroplating was chosen to form the first layer as a matter of convenience, as only a conductive surface was required and no pretreatment of the Cu substrate was necessary. The conditions for the formation of each layer, Table III, and specifically the electroplating potentials, were slightly different for each layer due to the system as well as changes in the electrolyte.…”

“…The clear presence of a modulated pentalayer structure demonstrates that HEED is a useful technique outside of alloying and deposition of metals with significantly differing standard electrode potentials, such as gold and nickel. 1 The successful production of multiple modulated pentalayer deposits from a single electrolyte suggests that additional and thinner layers could also be produced. The formation of Co(Ni-P)/Ni-P multilayer coatings have applications in both granting corrosion and wear resistance to plated surfaces in addition to forming new magnetic materials.…”

“…Application of a current for the electroplating portion of the HEED coatings was carried out using a system composed of a Keithly 2200-20-5 Programmable Power Supply 20 V 5 A, and two Keithly 2100 6 1/2 Digit Multimeter. 1 Measurements from the multimeters were recorded using Keithly Instruments Tool (Version 2.02) software. In order to ensure that electroplating played no role during the electroless deposition phase of HEED, the electroplating circuit was mechanically disconnected immediately after the termination of each electroplating phase.…”

“…The recent development of hybrid electro-electroless deposition (HEED) 1 has provided a means to produce several interesting multilayered deposits which were previously unavailable using a single bath. Broadly put, HEED is described as any single electrolyte in which one metal/alloy is the target of electroplating while another metal, or compositionally different alloy, is the target of electroless plating.…”