Pulse rectifier plating principle:
Pulse rectifier plating is a powerful tool to control metal outer tank electrodeposition. It uses the time function to improve the physical and chemical properties of the plating coating film by changing the pulse parameters, to achieve savings in precious metals and obtain a functional electroplating coating film purposes. Pulse rectifier electro plating belongs modulation current plating, its current is a fluctuation or on/off DC rush current, therefore, is essentially on-off DC plating. There are a variety of pulsed current waveform, commonly as square wave, triangle wave, sawtooth, order staircase wave etc.. However, in application situation, typical pulse power generated square wave pulse current is widely used.
Modulated current plating:
Conventional electroplating is generally used in the form of direct current, referred to as DC. DC current is a current direction continuous steady and does not change with time changing. DC current waveform common as single-phase half-wave, single-phase full-wave, three-phase half-wave, three-phase full-wave, DC or steady current, etc.. While to generate these waveforms power supply are, silicon-controlled rectifier, high-frequency switching power supplies. DC current with features of continuity or continuity, without interruption to control plating coating film outside the bath. Such as DC current increase cathode current density, inhibit side reactions and reduce the content of impurities in the electroplating coating, to improve current distribution, etc. are useless.
DC current after pulsing signal or other modulating alternating signal is called as modulation current, as well as the plating process under condition of modulation current is carried as modulation current plating. Modulated current plating mainly generated and existed to play a role to control outside bath plating coating quality. It can get the effect that the DC current plating can not achieve. For example, the pulse plating increase several times or even ten times more than direct current plating cathodic density, and get more detailed crystalline coating. Modulation current normally has pulse plating, asymmetric exchange electroplating, DC overlay plating cycle for the several forms of direct plating and so on.
Current pulse plating is actually used by a DC on-off, but when on DC peak current equivalent more than ordinary DC current times or even tens times. it is this high instantaneous current density make the metal ions in the very high overpotential to reduce, so that the grains become fine deposit layer. Pulse rectifier plating is widely used in electronic circuits of the electronics industry, connectors, printed circuit, electroplating integrated framework, the stem, etc., these products can be greatly improved the performance of electronic devices, and significant saving precious metals. Pulse rectifier plating is currently the most widely used and one of the largest gains modulation current plating.
Electropolishing - A Smooth Shiny Finish
Electropolishing - OverviewOur Electropolishing process cleans and polishes stainless steel in a special electrochemical solution. Electrical current passes through a chemical bath, dissolving a small amount of metal from the surface, leaving a smooth, shiny finish. The current is greatest on the outside edges and corners of parts, which are left especially smooth. Increasing the process time will remove more metal. Holes can be enlarged, threads can be rounded, and sharp edges or burrs can be reduced. Electropolishing is an excellent finishing process for fine parts because no vibrating or tumbling is involved.Because the part is bathed in oxygen, hydrogen is removed from the surface, thereby acting as a stress relieving anneal. In addition, the electropolished surface is free of hydrogen which greatly reduces the possibility of bacterial growth. Electropolishing is the best choice when contamination can not be tolerated.Electropolishing can be performed on Nitronic 60 and on 17-4 and 300 series stainless steel. We are not setup to electropolish 400 series stainless steel parts.
Components subjected to repeated stress, such as springs and delicate stampings, have a tendency to prematurely crack and wear. Removing surface defects by electropolishing may prolong service life. Electro polishing can salvage oversized gears and splines – which often “grow” during heat treating – by restoring them to their original size.
Electropolishing is ideal for medical devices and dental devices. Other applications include: food processing and food handling equipment, semiconductor equipment, springs, delicate stampings, gears and splines. Electro polishing is not right for every part, so it is important to consult one of our application specialist about new applications you are considering.
Electropolishing - Features
Electropolishing's primary function is to improve parts cosmetically. It cleans, polishes and brightens stainless steel in a way that no other process can and also removes small burrs. The results, easily visible to the naked eye, make extra finishing operations and costs unnecessary. Intricate components requiring microfinishes are greatly improved. As a result, friction, leakage and wear problems can be eliminated.
Stainless steel, although known for its excellent corrosion resistance, may still corrode when impurities are left on the surface of the metal. Electro polishing dissolves a minute layer of the part's surface metal. Impurities are removed and the surface is left brighter, ultra passive and protected from rust.
Aluminum Anodizing for the Medical Industry
The Electrolizing Corporation of Ohio provides the safest non-burning hard anodizing process for hardcoating aluminum. Our aluminum anodizing produces superior wear and abrasion resistance, compared to conventional hardcoat, and it is available in several different colors. Unlike plating, which is 100% buildup, ECO's aluminum anodizing is 50% penetration and 50% buildup.
Typical applications of aluminum anodizing include:
• Surgical Cases & Trays • Surgical Instrument Handles • Dental Components • Jet engine control valves, pistons and gears
• Race housings for bearings • Screw threads for hydraulic jacks • Aircraft landing gear components • Spraying systems & equipment
• Marine and architectural hardware • Medical handling and processing equipment • Textile machinery • Nuclear equipment
• Food processing & handling equipment
Our hard anodizing process is the hardest anodic coating available, with greater abrasion resistance than conventional anodizing. Thicknesses range from .0001 - .003” (.00254 - .0762 mm) on many alloys, and meet abrasion resistance requirements of MIL-A-8625F Type III.
You can color-code parts to simplify assembly procedures and to reduce assembly and installation errors, or to enhance the appearance of trim and decorative hardware.
Aluminum Alloys for Anodizing
Anodizing is recommended for virtually all aluminum alloys. Difficulties can arise if an order of components is manufactured from different alloys, and this is not made known to the anodizer. Each aluminum alloy has a different rate of penetration and buildup. If different alloys are processed together, different thicknesses of oxide are formed on the different alloys. This can result in "out of tolerance" components.
Both Reynolds and Alcoa make high-stability tool plate (wrought and cast, respectively). Maximum practical coating is .0025 - .003” (.0635 - .0762 mm).
Sandcast Alloys. The most commonly used are 155, 156, 319 and 356, with 356-T6 used most often. The maximum practical coating is .003” (.0762 mm). Grinds and polishes very well. The porosity produced by sandcasting can cause pits in the coating, which hard anodizing will not fill.
Die Cast Alloys. The most commonly used are 218, 360, and 380, gray. The maximum practical coating on 218 is .0002” (.00508 mm); for 360 and 380 the maximum practical coating is .001” (.0254 mm). 360 and 380 are not as wear resistant as 218. Only 218 produces a hardcoat comparable to the hardcoat of wrought or cast alloys. The primary elements of die cast alloys 360 and 380 – silicone and copper – are detrimental to hard anodizing.
Important Facts About Aluminum Anodizing
Hard anodizing is not plating.
Hard anodizing works in two ways; it penetrates the part’s surface and it builds up a layer on the part’s surface.
The depth of penetration and amount of buildup are approximately equal, but can vary according to the aluminum alloy. The term “thickness” includes both the amount of penetration and the amount of buildup.
Hard anodizing a shaft .002” (.0508 mm) thick will increase the diameter of the shaft by .002” (.0508 mm). Plating the same shaft .002” (.0508 mm) thick would increase the diameter by .004” (.1016 mm), since plating is 100% buildup.
Before machining components, be sure to allow for the hard anodizing buildup, not a plating buildup.When you specify hard anodizing, use the term “buildup per surface” to make clear what you are requesting.
Exacting dimensions can be maintained with hard anodizing. Standard commercial tolerance is± .0002” (.00508 mm) on a coating thickness of .002” (.0508 mm).
The formula for cutting a “V” thread prior to anodizing aluminum is buildup per surface multiplied by 4. This will equal the pitch diameter (PD) change. A typical example: desired PD = .4050”/.4091” (7/16 NF internal thread) and coating thickness of .0018” - .0022” (.0009” - .0011” buildup per surface). Maximum PD change will be .0011”x 4 = .0044”. Minimum PD change will be .0009” x 4 = .0036”. Therefore you should machine the pitch diameter to .4094”/.4127” to allow for the anodize buildup.