Metallizing

Metallizing is the general name for the technique of coating metal on the surface of objects. Metallic coatings may be decorative, protective or functional. Metallizing is the general name for the technique of coating metal on the surface of objects. Metallic coatings may be decorative, protective or functional. Techniques for metallization started as early as mirror making. In 1835, Justus von Liebig discovered the process of coating a glass surface with metallic silver, making the glass mirror one of the earliest items being metallized. Plating other non-metallic objects grew rapidly with introduction of ABS plastic. Because a non-metallic object tends to be a poor electrical conductor, the object's surface must be made conductive before plating can be performed. The plastic part is first etched chemically by a suitable process, such as dipping in a hot chromic acid-sulfuric acid mixture. The etched surface is sensitized and activated by first dipping in tin(II) chloride solution, then palladium chloride solution. The processed surface is then coated with electroless copper or nickel before further plating. This process gives useful (about 1 to 6 kgf/cm or 10 to 60 N/cm or 5 to 35 lbf/in) adhesion force, but is much weaker than actual metal-to-metal adhesion strength. Silver Reduction Metallization involves the spraying of a silver nitrate solution with other reducing chemicals that allow the silver to plate out onto a prepared surface at exceptionally high speeds offering the lowest cost, highest mass production volumes and yielding the highest quality metallized product available. Silver reduction uses real silver as the metal as opposed to the vacuum process which deploys aluminium. Silver reduction, as compared to vacuum metallization (which is a 'batch' process) is able to offer continuous production of the highest quality metallized product at the fastest production rates with the most advantageous cost structure and tightest lot to lot consistency when matching color. Silver Reduction Process video: https://www.youtube.com/watch?v=pmxRHFQDzt0 (courtesy of I.V. Miller & Son, Inc. - Miller Metallizing & Coating) Vacuum metallizing involves heating the coating metal to its boiling point in a vacuum chamber, then letting condensation deposit the metal on the substrate's surface. Resistance heating, electron beam, or plasma heating is used to vaporize the coating metal. Vacuum metallizing was used to deposit aluminum on the large glass mirrors of reflecting telescopes, such as with the Hale telescope. Thermal spray processes are often referred to as metallizing. Metals applied in such a manner provide corrosion protection to steel for decades longer than paint alone. Zinc and aluminum are the most commonly used materials for metallizing steel structures. Arc Spray In the arc spray process, the raw material in the form of a pair of metallic wires, is melted by an electric arc. This molten material is atomised by a cone of compressed air and propelled towards the workpiece. The molten spray solidifies on the component surface to form a dense, strongly adherent coating suitable for Corrosion Protection or component Reclamation. Sprayed coatings may also be used to provide Wear Resistance, Electrical & Thermal Conductivity or Free Standing Shapes. Major advantages of the arc spray process are that the coatings are available for almost instant use with no drying or curing times and there is no risk of damaging the component. In addition, the deposits possess a higher degree of bond strength than most other thermally sprayed deposits and the use of compressed air and electricity alone mean more economic coatings. Flame Spray is a process that uses an oxy-fuel flame to melt wires and in some cases powders or ceramic rods. The molten material is then atomised with compressed air to create a spray stream that applies the coating onto the surface being sprayed.