The success of chromium plate in industrial applications may probably be attributed to its unique combination of properties not possessed by any other one material available commercially. The most important of these are hardness, adhesion, corrosion resistance, non galling and non wetting qualities, and low coefficient of friction. In many instances all these properties are important for successful commercial applications.The hardness alone would not be sufficient to secure widespread use, become a number of other hard chrome materials or hardening process are available. It is the combination of very great hardness with extremely good corrosion resistance (equal or superior under most conditions to that of such noble metals as gold or platinum), and very low coefficient of friction or unique surface qualities, which has given such remarkable result in many applications of chromium plating.
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 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.
Many attempts have been made to produced "black chrome" 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. Modification of this process for "black" chromium plating has been proposed. Current interruption and sulfate-free chromic acid with fluoride or complex fluoride catalyst have been used.
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.
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 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.
Many attempts have been made to produced "black chrome" 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. Modification of this process for "black" chromium plating has been proposed. Current interruption and sulfate-free chromic acid with fluoride or complex fluoride catalyst have been used.
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.