Surface Finishing-Electroplating your Major Design Project

January 23rd, 2010 → 8:05 pm @

Students often choose to use mild steel for the manufacture of their Major Design Project. Mild steel tends to form rust after a very short time and really needs to have a protective surface finish applied. There are a number of surface preparations which include painting, electroplating to mention but a few.
Many students may be unaware of the techniques used to electroplate a metal object.
The process of electroplating takes place as metals in ionic form move from a positive to negative electrode. An electric current passing through the solution causes objects at the cathode or work piece to be coated by the metal in the solution.
Electroplating is done for many reasons, usually to beautify, insulate or to protect and to increase the corrosion resistance, conductivity solder ability of metal objects. Plating protects by one of two ways, either sacrificially or mechanically. Zinc and cadmium protect the base metals they cover sacrificially. They are more reactive to corrosion than iron or copper alloys so they corrode first, before the base metals. Copper, nickel, chromium and most other metals protect the base metals mechanically. They protect the base metals by forming a protective coating, therefore the protection is good only as long as that coating is intact. If there is defect or break in the protective coating the base metal will corrode before the plating. The most common metals used in plating are copper, nickel, gold. silver, chrome, zinc and tin.
Copper Plating, is the most common of all metals to be plated on to another metal. It’s finish is soft, red, ductile and solder able. It is seldom used as a final plate because it tarnishes easily. Copper is an excellent choice as an under plate since it is easy to buff or polish and it will cover small imperfections on the surface. A high polish on the copper helps to give your next layer a good appearance. Copper is highly conductive and makes a great coating for printed circuit or over steel wire that is used to conduct electricity. Copper is often used as a base for a conduct coating when electroforming. Copper has a high plating efficiency resulting in excellent coverage over difficult surfaces. It is about the only metal that will plate over zinc diecast.
Nickel Plating, is a yellowish white, hard, reflective finish used for wear resistance, solder ability, or dimensional restoration. Nickel plate often used over copper and under chromium for a decorative finish. Nickel is a very hard metal with poor ductility, therefore parts that are to be plated with nickel should be bent into their final shape before plating whenever possible. Nickel should be plated over copper before gold plating to reduce the corrosion or darkening of the gold.
Silver plating, besides being decorative, has the highest electrical and thermal conductivity of any metal. In most cases it is plated out looking white or pickled and can be polished with silver polish to bring out a shine.
Gold Plating, is sometimes made in different karat colors such as 14kt, 18kt, and 24kt. With Dalmar gold plating solution it is a 24kt gold but can be plated in different shades of gold by controlling the amount of power that you use.
Chrome Plating, or chromium plating as it sometimes is called has a blue-white color that may be applied over copper and nickel for decorative purposes. It may be applied directly on the base metal for engineering purposes. Chrome plating may be either shiny or dull and tends to highlight imperfections the same way that a painted surface will still show scratches and such after painting if proper preparation isn’t taken. For decorative purposes the finish or shine that is on the nickel will determine the finish on the chrome.
There are many very good web sites which can assist you setting up a home electroplating facility for you project. The cost of setting up need not cost you an arm and a leg.
Good luck with your project.

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