What is Electrophoresis / E-coating?

what is E-coat?

E-coat is a process that was first pioneered in 1930. Through many years of exploration and industrial use, it has become one of the preferred methods of metal finishing worldwide.

We create a stable E-coat emulsion, containing a mixture of organic resins and DE-ionized water. A DC voltage is then applied through the solution via two electrodes. This causes the electrolysis of water, with oxygen being liberated at the anode (positive electrode), and hydrogen being liberated at the cathode (negative electrode). Through this liberation of gases, the hydrogen ion equilibrium that immediately surrounds the electrodes is disturbed. As a direct result, there is a pH change in the solution causing a DE-stabilization of the paint components which creates a controlled precipitation.

As e-coat specialists, we have direct control over this reaction. Through manipulation of the electropaint chemistry we can change the characteristics of this precipitation or ‘coating’ to create a finish that matches the customer requirement.

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A Brief History of E-coat

Origin
Even though E-coat has been with us since the 1930, it is mainly due to large interest and capital investment in the 70's by the automobile industry for primers that made it popular. Since then the technology has found its way into the more decorative and functional (non primer) single coat application like CLEARCLAD.

Timeline

1940's		-		Experimentation into electodepositing phenolic resin coatings onto electrical wire on a continuous basis.
1950's		-		Full scale development of electrodeposition of anti-corrosive paint primers onto automobile bodies.
1960's		-		Development of exterior durable, light colored electropaint resin systems suitable for domestic appliances, architectural aluminum etc.
	(Principle technology so far - anodic)
1970's		-		Cathodic technology displaces anodic as the principle system in the automobile industry. Such systems are adapted for small scale use in the electroplating industry (circa 1978).
1980's		-		Technology continues to evolve as protective coatings for the metal finishing industry.

So, what is E-coat?

Process Mechanism

E-coat is an emulsion of organic resins and de-ionized water, which is in a stable condition. The e-coat solution also comprises of some solvent and some ionic components. When a D.C. voltage is applied across two immersed electrodes, the passage of current is accompanied by electrolysis of water. This results in oxygen gas being liberated at the anode (positive electrode) and hydrogen gas liberated at the cathode (negative electrode). The liberation of these gases disturbs the hydrogen ion equilibrium in the water immediately surrounding the electrodes. This results in a corresponding pH change and this in turn de-stabilizes the paint components of the solution and they coagulate onto the appropriate electrode.

-		Cathodics electropaints are stable except at high (alkaline) pH. Anodics are stable except at low (acid) pH
-		Electrolysis of water causes the cathode to become alkaline and the anode to become acid.

Electrolysis of Water

Electrophoresis is a well documented process whereby electrically charged particles in a conductive medium will migrate to the electrode bearing the opposite charge under the influence of D.C. voltage. Although many technical descriptions of electropaint ascribe electrophoresis to the deposition process it is not the predominant mechanism. However, it is very common to refer to electropaint as "Electrophoretic"

How is it applied-Application

An unfinished product is immersed in a bath containing the electrophoretic paint emulsion, and then an electric current is passed through both the product and the emulsion. The paint particles that are in contact with the product adhere to the surface, as described in the above mechanism, and build up an electrically insulating layer. This layer prevents any further electrical current passing through, resulting in a perfectly level coating even in the recessed parts of complex-shaped goods. The product is then removed from the paint bath and baked in an oven.

How does this compare to plating

Due to the insulating nature of the deposit as described above, it is possible to accurately control the thickness over the part. Whereas with plating and anodizing thickness is controlled by amp/time relationship;

E-Coat vs. electroplating and anodizing - amp/time relationship.

With e-coat the thickness is controlled by voltage. Time is not as critical, as once the part is coated and insulated, no more coating will take place. Depending on surface area and complexity of the parts, most coating is easily accomplished with 2 minutes. This highlights one of the big equipment differences. Plating and anodizing require low voltage and high amperage rectification. E-coat requires high voltage and low amperage (1 sq. ft. draws 1.5 amps max) rectification.

What is electroplating?

What is electroplating?

Electroplating (often just called "plating") is the deposition of a metal coating onto an object by putting a negative charge on it and putting it into a solution which contains a metal salt. The metal salt contains positively charged metal ions which are attracted to the negatively charged object and are "reduced" to metallic form upon it.

How does plating work?

Look at the figure above: We have a metal object that we want to plate with another metal. First we fill a "cell" (a tank, vat, or bowl) with a solution of a salt of the metal to be plated. Most of the time the salt (nickel chloride in our example) is simply dissolved in water and maybe a little acid.

In this example, the NiCl₂ salt ionizes in the water into Ni⁺⁺ ions and two parts of Cl^- ions.

A wire is attached to the object, and the other end of the wire is attached to the negative pole of a battery (with the blue wire in this picture) and the object is immersed in the cell. A rod made of nickel is connected to the positive pole of the battery with the red wire and immersed in the cell. The battery is pulling electrons away from the nickel anode (through the red wire) and pumping them over to the object to be plated (through the blue wire)

Because the object to be plated is negatively charged (by being connected to the negative pole of the battery and having electrons pumped to it), it attracts the positively charged Ni⁺⁺ ions that are floating around in the solution. These Ni⁺⁺ ions reach the object, and electrons flow from the object to the Ni⁺⁺ ions. For each ion of Ni⁺⁺, 2 electrons are required to neutralize its positive charge and "reduce" it to an atom of Ni⁰ metal. Thus, the amount of metal that deposits is directly proportional to the number of electrons that the battery provides.

Bright Nickel Plating

Bright Nickel Plating

Nickel Plating Process

highly ductile deposits which are free from laminations. It produces brilliant, white deposits of high clarity, reflectivity and depth. The deposit is active and can be chromium plated if specified. This nickel plating porcess can be used in barrel applications as well as cathode rod and air agitated rack installations.

It is a process that plates faster with more coverage in the low current density area. It produces 20 to 30% more nickel thickness in the lower current density area than any other nickel system. Therefore, you also get better chrome coverage in the low current density than any other nickel process.

Because it is a single maintenance additive process, eliminates plating variations common with multi-additive bright nickel processes. There will be less of a chance for operator-caused imbalance of brighteners and additives. Can also be used as a conventional index system with a separate carrier, brightener, indexer and leveler.

Alkaline Non-Cyanide

Alkaline Non-Cyanide

is a unique non-cyanide alkaline copper plating process.

Today, American cyanide copper platers face Department of Homeland Security (DHS) regulations in reporting potassium and sodium cyanide. cyanide and the DHS regulations of reporting cyanide.

the first with a heavy production proven, non-cyanide, non-pyrophosphate, alkaline copper plating process . It does the “impossible” by plating directly onto steel, brass, copper, stainless steel, zincated aluminum, electroless nickel, sulfamate nickel as well as diecast zinc surfaces with out a separate strike. Ultra Cu copper has outstanding adhesion to difficult-to-plate die-cast zinc surfaces. The single additive bath produces superior results in both barrel and rack installations as either a strike or plate bath. It covers better and has greater throwing power than cyanide copper.

Acid Copper Plating

Acid Copper Plating is a new and unique single additive acid copper plating process which has shown to provide superior plate distribution by plating more copper in lower current density areas and reducing the copper thickness in higher current density areas. The ratio of plating thickness between high current areas and low current areas is a low 4:1. A significant advantage is reduced consumption of anodes when Ultra AC is plated at the same thickness of copper in the LCD as with other processes.

With the greater thickness in the LCD, cut-through when buffing and polishing the copper plate is virtually eliminated.

Click here for additional information on “How to Decrease Cut Through & Reduce Anode Consumption” with Brite Acid Copper Plating..

ELECTRO PLATING

Gold plating is the process of adding a thin layer of gold to another metal in order to give that metal a gold-like appearance. In most cases, the layer of gold is very thin, just enough to cover all exposed surfaces of the other metal. It is commonly used in decorations and in jewelry plating.

The benefit of gold plating for jewelry is that it gives the look of gold, but does not have the cost of gold. In jewelry applications, a gold plating is most commonly applied to silver. Thus, the jewelry actually includes two precious metals, rather than just one.

while many may commonly associate gold plating with jewelry, it is not the only application for the practice. Gold plating is also commonly associated with electronic applications. This is done to allow better conductivity and make things resistant to abrasion and wear, along with other benefits.

Gold plating can be accomplished in a number of different ways, including electropalting. This is done by putting the object being plated, the cathode, into a solution, usually water. It is connected to the negative side of a charge, such as a battery. Then, the donor for the plating, the anode, is also placed in the solution connected to the positive side of the charge.ionization occurs and the anode slowly dissolves, with the positively-charged ions in the metal going to the negatively charged product.

However, gold plating, like most types of metal finishing, can be done in a number of other ways. The gold metal can be suspended in a solution, which is then brushed on the object being plated. The goal is to maximize the effect but to minimize the amount of gold needed to do the job. This is a very low-tech solution that may be used by those doing small jobs privately.

Due to the fact that gold is such a soft metal and the layer over jewelry products is so thin, there will likely be a time when the gold plating becomes worn in spots. Jewelry, especially those pieces worn daily, tend to take a substantial amount of abuse. Taking such items to a jewelry repair shop is the best way to restore them to their original luster. This type of repair is usually very inexpensive and may even be included in some service policies.