Electroplating uniformity

Indium chemicals and electroplated metal deposits ate replacing mercury (qv) in the manufacture of alkaline batteries (qv). Indium, like mercury, functions to reduce outgassing within the battery and promotes the uniform corrosion of the anode and cathode while the battery is under electrical load. Indium inorganic chemicals also find use as catalysts in various chemical processes. 

In a similar procedure, the atomizer test, which depends on the behavior of an advancing rather than a receding contact angle, a fine mist of water is apphed to the metal surface and the spreading of water is observed. On a clean surface, water spreads to a uniform film. With oleic acid as the test soil, the atomizer test can detect the presence of 10 mg of soil per cm, less than a monomolecular layer (115). For steel that is to be electroplated, the copper dip test is often employed. Steel is dipped into a cupric salt solution and the eveimess of the resulting metallic copper deposit is noted. 

For large Wa, the current distribution is uniform. For example, when electroplating (qv) an object, usually a uniform deposit is desirable. Equation 35 suggests that a larger piece, ie, low Wa, would be more difficult to plate uniformly than a smaller one. 

Some electroplating solutions produce more uniform deposits than others, and the ability of a solution to deposit uniform coatings is measured by its throwing power (see Section 12.1). 

Articles of complex shape may be impossible to electroplate satisfactorily, and electroless nickel (see Section 12.5) may be useful in providing a relatively uniform protective coating. Even so, the considerations of access of cleaning and process solutions, and retention/draining of all process solutions, still apply. 

The effects of mercury film electrode morphology in the anodic stripping SWV of electrochemically reversible and quasi-reversible processes were investigated experimentally [47-51], Mercury electroplated onto solid electrodes can take the form of either a uniform thin film or an assembly of microdroplets, which depends on the substrate [51 ]. At low sqtrare-wave frequencies the relationship between the net peak crrrrent and the frequency can be described by the theory developed for the thin-film electrode because the diffusion layers at the snrface of microdroplets are overlapped and the mass transfer can be approximated by the planar diffusion model [47,48],... 

Electroplating of one metal onto another is widely used for protection against corrosion and wear or for cosmetic purposes.16 Again, the source of metal for deposition could be anodic dissolution or a prepared solution with an inert anode. In contrast to electrolytic refining, only a very thin layer (typically on the order of 1 to 10 pm) of the plating metal is wanted, but usually this layer must be uniform, cohesive, and nonporous, and often a shiny appearance is desired. To understand the roles of some of the variables in electroplating, it is useful to consider the electrodeposition... 

Finally, metal objects can sometimes be fabricated in their entirety by electrodeposition (electroforming), with much the same considerations as electroplating. Conversely, portions of a metal specimen can be selectively electrolyzed away (electrochemical machining). This technique is especially useful where the metal to be shaped is too hard or the shape to be cut is too difficult for conventional machining. The sample is made the anode, a specially shaped tool the cathode, and electrolyte solution (e.g., aqueous NaCl) is fed rapidly but uniformly over the surface to be machined. Current densities may reach several hundred amperes per square centimeter across the electrolyte gap of a millimeter or so. Excellent tolerances can be achieved in favorable circumstances.16... 

The majority of commercial electroplating involves an aqueous medium hence, depending on the pH of the solution, the metal ions will be present in the bath as aquo or hydroxo complexes. In many cases another complexing agent, usually cyanide, is added. Such baths are operated under alkaline conditions to prevent the release of HCN. The choice of a particular bath composition is determined by technical factors.Thus, for example, zinc—alkaline cyanide baths have an excellent macroscopic throwing power, that is the ability to produce a uniform plated surface on a substrate that has macroscopic irregularities. 

In this protocol we describe an electroplating procedure for mild steel with an adhesive aluminum layer in Lewis acidic ionic liquid l-ethyl-3-methylimidazolium chloride [EMIMJC1 containing AICI3. We aim to electroplate mild steel with dense, adherent and uniform aluminum layers in the employed ionic liquids at room temperature. 

In shielding for radio-frequency and electromagnetic interference an electroplated coating may -not be necessary. Highly effective performance can be obtained with deposits of thickness as low as 2 to 3 /on and these can be applied economically by electroless processes, which give very uniform thicknesses of deposits even in recessed areas. 

---