E-coating is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field. It is ultimately caused by the presence of a charged interface between the particle surface and the surrounding fluid.
It is the basis for a number of analytical techniques used in chemistry for separating molecules by size, charge, or binding affinity.
E-Coating: The Definitive Guide
In the modern-day, the demand for high-quality and durable products among customers and end-users is immeasurable.
The expectation is for the products to perform well, demonstrate reliability and exemplary surface finish with better corrosion resistance.
E-coating is one of the several processes designed to meet all these market demands on different products accordingly.
E-Coating Basics
E coated die cast part
E-Coating refers to a process where electrically charged particles are deposited out of a substrate suspension to coat a conductive part.
Mostly, it is known as electrophoretic coating, and it involves use of wet paint finishing intended to prevent metallic surfaces from corrosion.
You can use this coating process on different metals in various applications such as auto parts, hardware, and jewelry among others.
E-coating process is largely available commercially in a black hue, but you can also get it in other colors, albeit less common.
During electrocoating process, you apply paint to a part at a set film thickness, often controlled by the amount of voltage applied.
The applied coating insulates the part electrically since the deposition is self-limiting and tends to slow down in the process.
Benefits Of E-Coating
E-coating offers a wide range of benefits that cut across different aspects such as cost-efficiency, eco-friendliness, and in-line productivity among others.
Ideally, this coating method guarantees immense cost-efficiency in several elements.
For instance, it provides higher transfer efficiency, requires relatively low manpower, and guarantees accurate film build control.
Regarding environmental benefits, electrocoating produces zero or low VOC and HAPs products.
Besides, the process hardly produces heavy metal products, and this is essential since it reduces worker’s exposure to hazardous substances.
Moreover, it guarantees minimum waste discharge and reduces fire hazards.
When it comes to benefits in enhanced line productivity, this coating technique offers faster line speeds, which increases throughput.
It also reduces a significant amount of human error since most parameters are automated.
Besides, it allows non-uniform line loading, which is vital in increasing overall productivity.
How E-Coating Process Works
This process is divided into the following four distinctive steps;
E-coating process
1) Pretreatment
It involves cleaning the metal surface and applying phosphate to it to ensure it is ready for the respective e-coat.
Ideally, pretreatment is fundamental to attaining performance requirements the product end users desire.
The manufacturer assesses the metals to be processed and selects suitable chemicals for phosphating and chemical cleaning.
2) E-coating Bath
In this stage, relevant coatings are applied on the pretreated metal surface inside an electrocoating bath.
The process uses an accurately calibrated process control machine.
Ideally, the e-coating bath consists of 10-20% of solid paints and about 80-90% of deionized water.
In this case, deionized water acts as a paint solids carrier, which is always under unending agitation.
Paint solids consist of resin and pigments.
3) Post-rinsing
The essence of this stage is to improve the coating quality and to trigger recovery of excess paint.
Paint is applied to a part using a controlled voltage amount to attain the ideal film thickness.
Immediately the coating attains the desired thickness; the part insulates and prompts the process to slow down.
Paint solids clinging to the surface are rinsed off to keep aesthetics and application efficiency as the part exits the bath.
The residue material is known as cream-coat returns to the tank allowing the e-coat process to attain efficiency rates of above 95%.
4) Bake Oven
Once the e-coated part exits the post-rinsing stage, it is placed inside a bake oven to cure and cross-link paint film to optimize its performance properties.
You can bake it for about 20 minutes with a part temperature of about 375°F for most e-coating technologies.
E-Coating Vs Powder Coating
Ordinarily, both e-coating and powder coating processes guarantee immense protection for metal surfaces.
Besides, they are based on more or less same principle of electrodeposition.
In both processes, a coating is applied to a substrate to enhance corrosion resistance and enhance wear resistance.
Moreover, it comes in handy in promoting adhesion.
Even so, e-coating is regarded more of a wet process, whereas powder coating is considered a dry process.
Essentially, powder coating electrifies powder paint elements, while e-coating entails immersing the object surface liquid paint pool for electrification.
Thus, thickness of coating in e-coating is dependent on amount of electric current applied to the liquid.
And this forms a highly accurate and even coating thickness and film layers.
Materials Used In E-Coating
Ideally, electrocoating elements are made from different substances such as pigments, polymeric resin, and solvents or diluents.
However, polymeric resin makes the better part of final paint and offers features such UV protection and corrosion resistance.
The essence of pigment is to provide color, corrosion protection, and gloss.
Deionized water makes up about 80-90% hence a major component of an e-coating bath.
It acts as a paint solids carrier consisting of pigments, resins, and solvents.
Solvents are vital in ensuring smooth film appearance and application.
Primarily, electrocoating products are known as either anodic or cathodic to indicate the specific place where deposition occurs.
When To Consider E-Coating
Technically, e-coating process comes in handy, especially when coating relatively hard-to-reach surfaces.
You can always use a thinner coating thickness, and the liquid immersion still gets to such surfaces evenly and easily.
Thus, it is an ideal option to consider when you want to attain a uniform paint coat on some surfaces that seem quite difficult to reach.
E-coating is also a suitable option if you are painting an object to use in relatively harsh environmental conditions.
Essentially, this coating process is quite durable and prevents surface corrosion, thus ideal for parts designed for aggressive applications.
You also need to consider e-coating in large-scale production.
Technically, this process is quite efficient, fast, and cost-effective, thus suitable when coating several parts.
Cost Of E-Coating
Ideally, e-coating is regarded as the lowest-cost finishing application.
However, it is imperative to always look beyond material cost per square foot when determining the actual cost of e-coating process.
Some fundamental factors that influence the overall cost of this part painting process include the following;
E coated parts
Production Volume
Ordinarily, many manufacturers are increasing annual production quantities to a substantive volume.
As such, electrocoating is gradually becoming a preferred coating technique suitable for the large production volume.
E-coating achieves dense rack loading, making it easy for manufacturers to attain the necessary cost-efficiency in the process.
Capital
Mostly, e-coating lines need more investment capital since the equipment, and related elements are quite costly.
However, after considering other cost variables, you’ll notice the process yields cheapest coating on parts.
Paint Material
When comparing applied paint materials, e-coating is often the most cost-effective option.
It allows high transfer efficiency of about 95-98% and has a self-limiting ability of the process leading to a differential of about 0.2 mils deposited paint film.
Part Complexity
Parts are available in different shapes and sizes.
However, this coating technique seems more cost-effective since the part surfaces get an even film thickness.
Thus, it reduces the cost of this coating irrespective of the complexity part.
Energy
Ordinarily, liquid and powder lines need daily rack cleaning, pretreatment, and additional dry-off.
Moreover, a suitable environmental room is also necessary for the lines to maintain air quality for even paint application.
Besides, e-coating also has its share of energy requirements.
However, the energy disparities are relatively insignificant when all factors are considered.
Miscellaneous Costs
In any e-coating process, additional overhead costs must always apply.
For instance, insurance and material handlers, among others, determine the actual cost of the process.
In a nutshell, e-coating is quite affordable than other coating technologies
E-Coating Technologies
Essentially, the classification of e-coating technologies is often based on their primary use as follows;
As A Primer
A popular primer technology often used in e-coating is cathodic epoxy electrocoat.
Ideally, it provides superior adhesion, corrosion resistance properties, and high compatibility with numerous powder and liquid topcoat materials.
It has better appearance properties and comes in handy in different single-coat applications where UV resistance is not a significant concern.
Most cathodic epoxy electrocoating materials are eco-friendly and suitable for parts with a possible cure temperature above 380°F.
Alternatively, you can use anodic epoxy electrocoat materials as a primer.
They provide better adhesion, corrosion tolerance and superior to most liquid paint primer materials often used.
It is suitable for components coated as assemblies and contains relatively heat-sensitive parts such as seals and bearings.
As A Topcoat
You can use cathodic acrylic e-coating materials in different topcoat applications since they are suitable for UV resistance.
They are ideal in single-coat applications and, in many instances, superior to most liquid primer, and topcoats paint systems.
This E-coating technology delivers ideal adhesion and corrosion resistance properties.
Environmental Impact Of E-coating
Electrocoating has an impact on the environment.
However, with an appropriate design of processing system and ideal equipment for supporting this process, it can completely comply with stipulated environmental regulations.
Coating technologies used in e-coating have advanced, and nowadays, most materials used do not contain heavy metals.
Moreover, waste management systems are in place from the pretreatment to the finishing stage.
The essence is to ensure released substances regarded as hazardous are kept at levels below the regulatory requirements.
At Inox, we use E-coating for all your die cast parts upon request.
Contact us now for competitive prices and quality finish.