Life Style and Technology

The Function of Wetting Agent

On electroplating practice we will see the bubble merge from the electrode, from the cathode or from anode can merge bubble that produce gas. As on a normal process like on water electrolize, cathode will produce hidrogen gas and anode will produce oxygen gas.

Bright Nickel Plating

The nickel baths for bright nickel to which brighteners, mainly bath-soluble organic compounds, are added, are mostly of the Watts type with widely varying proportions of chloride and sulfate. Boric acid is always present, usually not less than 35 g/l. Condition in the cathode film must be favorable not only for the deposition of nickel but also for the functioning of the brighteners function best at pH value of about 3 to 5 and bath temperatures of about 50 to 65oC.

The zinc coating of steel by hot dipping is confusingly known as galvanizing, although no use is made of electricity in the process. It provides a cheap and effective method of producing a good rust-resisting coating on steel sheet, steel wire and on miscellaneous fabricated steel and cast iron articles, such as tanks, vessels, hardware, pipes and fittings and structural components, most of which will be exposed to the weather, or to damp air or water.

Sealing the Oxide Film

The oxide films obtained after anodizing have considerable porosity and high adsorptive capacity. Sealing of the film increases their resistances to corrosion and improves their electrical insulating properties. Sealing is essential for films that have been produced by anodizing in sulfuric acid, because only after sealing do the film acquire a sufficiently high resistance to corrosion.

Nickel is one of the most important metals applied by electrodeposition. The plate is used principally as a bright coating underneath a much thinner chromium electroplate to provide a highly lustrous and corrosion-protective finish for articles of steel, brass, zinc die castings, chemically metalized plastics, and, to a much smaller extent, for coatings on aluminum and magnesium alloys.

Many Types of Chromium Plating

Hard Chromium Plating
The benefit of the hardness of chromium deposits is not effectively obtained unless the coating is deposited on a sufficiently hard basis metal and to a satisfactory thickness. Generally, hardened steel is used for the basis metal. Even a relatively heavy deposit of chromium may be crushed or indented if applied over a soft basis metal such as copper. The best possible adhesion is also important in many uses where the surface may be subjected to severe stress or shock, and any chipping of the deposit would be injurious.

Etch Prevention
The self-regulating baths have a disadvantage common to all baths containing fluorides or complex fluorides, a tendency to corrode or etch recesses which do not cover with chromium. This tendency to etching is especially noted on steel, commercially, the ordinary baths with sulfate catalyst hate a strong tendency to etch copper and brass. This etching tendency is especially marked in over catalyzed bath, and can be overcome to a considerable extent by keeping the bath in balance, or operating at as low a catalyst concentration as possible. In higher ratio of baths, overcome this etching by prefilming the surface to be plated as cathode in a plain chromic acid solution.

Porous Chromium Plating
This name have been given to modified chromium deposits with oil-retaining properties, used on internal combustion engine cylinders and piston rings. Such deposits were used especially during the war on aircraft and diesel engine cylinders for salvage and to make engines last longer. Three main of porous chromium plate have come into common use.

The first is the mechanical type, produce by grit blasting the basis metal, chromium plating, and finally finishing to size by grinding, honing, or polishing. The second and third types of plate are those with pitted and channel porosity. Both of the later are obtained by treating the chromium deposit in an etching solution. The type of porosity obtained depends on careful control and regulation of the condition of deposition. Numerous publications and patents describe the production of all these types of porous chromium plate and the result obtained with them.

Black and Color Chromium Plating
Many attempts have been made to produced "black" chromium plate, and such deposits have been used commercially. They are usually dark grey rather than black, however, and all dull or mat chromium deposits seem to turn bright metallic rather readily if exposed to much abrasion or wear, in spite of the hardness of the metal. Oiling and other final treatments give grey or dull deposits a blacker appearance. An early "black" chromium plate was produced by using a high current density in a cold bath containing principally chromic and acetic acids.

Chromium Alloy Plating
Chromium alloy plating can be considered a subheading under trivalent bath, there is almost no alloy plating possible from hexavalent solutions. There has been a great deal work, and some reviews are available, but nothing of commercial importance seems to have been developed. It appears likely that some fundamental problems of depositing chromium from trivalent baths remain to be solved, and that these are probably not made appreciably easier by introducing the added factor of alloy deposition.