| Plating Basics |
An Introduction to Barrel Plating
History and Brief Overview of Barrel Plating
The end of the Civil War saw the need for increased
production capabilities in the field of metal
finishing. To meet this demand, finishers began
using wooden "barrels" into which large amounts of
manufactured parts could be placed. The entire unit
was held on each end and immersed into a large
tank while rotating the barrel along its horizontal
axis. Electrical contact was made to an outside D.C.
power source to provide the energy for the plating
process to take place.
Rapid advances were made in the field of barrel
plating after WW II with the invention of chemically
resistant plastic materials for equipment
manufacture. These materials prevented not only
deterioration of the barrels but minimized the
solution absorption which used to occur in the
older style wooden cylinders .Thus the industry
took a giant leap into the modern era of metal
finishing.
History and Brief Overview of Barrel Plating
The end of the Civil War saw the need for increased
production capabilities in the field of metal
finishing. To meet this demand, finishers began
using wooden "barrels" into which large amounts of
manufactured parts could be placed. The entire unit
was held on each end and immersed into a large
tank while rotating the barrel along its horizontal
axis. Electrical contact was made to an outside D.C.
power source to provide the energy for the plating
process to take place.
Rapid advances were made in the field of barrel
plating after WW II with the invention of chemically
resistant plastic materials for equipment
manufacture. These materials prevented not only
deterioration of the barrels but minimized the
solution absorption which used to occur in the
older style wooden cylinders .Thus the industry
took a giant leap into the modern era of metal
finishing.
Toll Free: 1-800-280-3141
Email: info@goldnickel.com
Email: info@goldnickel.com
Functions of barrel plating
The primary function of barrel plating is to provide an economical means to
electroplate manufactured parts that also meets the customer’s specific finishing
requirements.
The four most important requirements are: Engineering applications, such as building
up the thickness of metal to change the physical size of a part or to provide a good
surface for some other treatment such as painting or screening. Decorative coatings
such as Bright Nickel, Brass, and Antiquing. Cosmetic uses such as Zinc plating to
improve shelf life and salability. But by far the most important use of barrel plating is
to extend the corrosion protection of the customers' parts.
Which parts should be barrel plated and why?
Barrel plating can accommodate a wide variety of shapes and sizes as well as
different metals and alloys. Generally any part that can fit in the barrel can be plated
provided good procedures are maintained. The quality of the finish can equal that of
rack plating and is usually more economical.
The rotation of the barrel and the parts within it lend themselves to other
advantages. The mechanical energy of the rotation produces a burnishing action that
helps to clean and de-scale the parts to a greater degree than rack plating, much the
same as wringing your hands under the water faucet facilitates the speedier removal
of soils and dirt from them. The tumbling action is also responsible for the high
degree of plating uniformity which can be achieved in the barrel. As the parts move
they make and break electrical contact creating what is called a bi-polar effect
whose net benefit is the evening out of the high and low areas which could pose
enormous problems if the same parts were to be racked and finished. It is for this
reason that fasteners are almost exclusively plated in barrels, as well as economics.
The Plating Barrel
The two most common types of barrels are the horizontal barrel which is a
hexagonally shaped cylinder and the oblique barrel which closely resembles a cement
mixer in both looks and operation. While the barrels may be made out of virtually any
material they are usually constructed of rigid polypropylene because of its chemical
resistivity.
In order to allow the plating solution to enter and exit the barrel without loss of the
parts to be plated, holes are drilled along each side of the barrel and the removable
panel called the door. The holes must be properly sized so that parts do not fall
through while being large enough for solution to easily drain to minimize wasted
chemicals. These sizes can include barrels with diameters of one (1) inch up to
monsters 24 inches wide by 60 inches long.
There are a number of different methods to carry the electrical current to the parts
one wishes to plate. By far, however, the most common way to supply current to the
parts is the "dangler". This is usually a coated cable with a large metal ball crimped
onto the end which terminates inside the barrel and simply rides on top of the parts
as they tumble in the cylinder. They enter the barrel through a hole machined out of
each end of the barrel and are then connected to the rectifier which will supply the
D.C. current to power the chemical process.
Barrel plating fundamentals and the production process
Parts need only to be free-flowing enough to enter the mouth of the barrel.
Generally, loads should not exceed half the volume of the barrel or improper tumbling
will occur and a loss of plating uniformity. Parts must be able to tumble freely to
insure a good plating distribution. Such interior protrusions as breaker bars, dimples
or ribbed sides should be used as necessary.
The rotation of the barrel while in the plating tank is also very important. Typically a
speed of 3 to 6 RPM is considered adequate but faster speeds, up to 60 RPM
facilitate a more uniform deposit even though there may be some physical wear on
the barrel itself. As long as the parts themselves will not be harmed it is more
desirable to maintain as fast a rotational rate as is practicable.
Barrel sizes and hole perforations should be chosen with care depending on the size
of the parts to be plated. Too small a hole will trap solution by capillary action and
drag the chemicals all along the plating line. Too small a barrel and the parts will not
tumble properly.
Typical plating cycle
1) Load parts and close barrel.
2) Place loaded barrel into hot alkaline cleaner tank and rotate 10-15 minutes to
remove oils and grease, then rinse in fresh water.
3) Rotate barrel in acid dip which can contain such chemicals as hydrochloric,
sulfuric, nitric acid, or dry acid salts. The purpose of these chemicals is to remove
any rust, activate the surface of the metal and neutralize any residual alkalinity left
on the parts from the cleaner tanks. Rinse thoroughly.
4) Now you are ready to plate the parts based on the needs of the customer. The
length of time in the plating tank is determined by the thickness of metal to be
plated. The greater the thickness the greater the time. As always, rinse when done.
5) Having plated the part you may now apply any number of post treatments
including but not limited to: oils, waxes, sealants, chromates or other metals such as
brass and chrome. Yes, you still must rinse.
6) Unload parts into a drying unit and dry completely at no greater than 120 degrees
F.
Quality Control
Proper and on-going training is extremely important to successfully barrel plating any
part. Records should be kept regarding all of the important parameters involved in
each step along the plating cycle. These should include things such as part
description, load size, voltage, time, thickness readings, chemical additions and any
problems which may have taken place during the cycle. All relevant data and notes
should be routinely reviewed to assure that the product will remain at a consistent
level of quality, can be repeated, and that the process can be continuously improved.
There are numerous quality systems which the customer may require the barrel
plater to employ such as the ISO 9000 standard which Merit has done. This will help
us to continue to achieve the highest level of customer satisfaction possible.
This information was reprinted and edited from Finishing.com and written by F. R. Zemo.
The primary function of barrel plating is to provide an economical means to
electroplate manufactured parts that also meets the customer’s specific finishing
requirements.
The four most important requirements are: Engineering applications, such as building
up the thickness of metal to change the physical size of a part or to provide a good
surface for some other treatment such as painting or screening. Decorative coatings
such as Bright Nickel, Brass, and Antiquing. Cosmetic uses such as Zinc plating to
improve shelf life and salability. But by far the most important use of barrel plating is
to extend the corrosion protection of the customers' parts.
Which parts should be barrel plated and why?
Barrel plating can accommodate a wide variety of shapes and sizes as well as
different metals and alloys. Generally any part that can fit in the barrel can be plated
provided good procedures are maintained. The quality of the finish can equal that of
rack plating and is usually more economical.
The rotation of the barrel and the parts within it lend themselves to other
advantages. The mechanical energy of the rotation produces a burnishing action that
helps to clean and de-scale the parts to a greater degree than rack plating, much the
same as wringing your hands under the water faucet facilitates the speedier removal
of soils and dirt from them. The tumbling action is also responsible for the high
degree of plating uniformity which can be achieved in the barrel. As the parts move
they make and break electrical contact creating what is called a bi-polar effect
whose net benefit is the evening out of the high and low areas which could pose
enormous problems if the same parts were to be racked and finished. It is for this
reason that fasteners are almost exclusively plated in barrels, as well as economics.
The Plating Barrel
The two most common types of barrels are the horizontal barrel which is a
hexagonally shaped cylinder and the oblique barrel which closely resembles a cement
mixer in both looks and operation. While the barrels may be made out of virtually any
material they are usually constructed of rigid polypropylene because of its chemical
resistivity.
In order to allow the plating solution to enter and exit the barrel without loss of the
parts to be plated, holes are drilled along each side of the barrel and the removable
panel called the door. The holes must be properly sized so that parts do not fall
through while being large enough for solution to easily drain to minimize wasted
chemicals. These sizes can include barrels with diameters of one (1) inch up to
monsters 24 inches wide by 60 inches long.
There are a number of different methods to carry the electrical current to the parts
one wishes to plate. By far, however, the most common way to supply current to the
parts is the "dangler". This is usually a coated cable with a large metal ball crimped
onto the end which terminates inside the barrel and simply rides on top of the parts
as they tumble in the cylinder. They enter the barrel through a hole machined out of
each end of the barrel and are then connected to the rectifier which will supply the
D.C. current to power the chemical process.
Barrel plating fundamentals and the production process
Parts need only to be free-flowing enough to enter the mouth of the barrel.
Generally, loads should not exceed half the volume of the barrel or improper tumbling
will occur and a loss of plating uniformity. Parts must be able to tumble freely to
insure a good plating distribution. Such interior protrusions as breaker bars, dimples
or ribbed sides should be used as necessary.
The rotation of the barrel while in the plating tank is also very important. Typically a
speed of 3 to 6 RPM is considered adequate but faster speeds, up to 60 RPM
facilitate a more uniform deposit even though there may be some physical wear on
the barrel itself. As long as the parts themselves will not be harmed it is more
desirable to maintain as fast a rotational rate as is practicable.
Barrel sizes and hole perforations should be chosen with care depending on the size
of the parts to be plated. Too small a hole will trap solution by capillary action and
drag the chemicals all along the plating line. Too small a barrel and the parts will not
tumble properly.
Typical plating cycle
1) Load parts and close barrel.
2) Place loaded barrel into hot alkaline cleaner tank and rotate 10-15 minutes to
remove oils and grease, then rinse in fresh water.
3) Rotate barrel in acid dip which can contain such chemicals as hydrochloric,
sulfuric, nitric acid, or dry acid salts. The purpose of these chemicals is to remove
any rust, activate the surface of the metal and neutralize any residual alkalinity left
on the parts from the cleaner tanks. Rinse thoroughly.
4) Now you are ready to plate the parts based on the needs of the customer. The
length of time in the plating tank is determined by the thickness of metal to be
plated. The greater the thickness the greater the time. As always, rinse when done.
5) Having plated the part you may now apply any number of post treatments
including but not limited to: oils, waxes, sealants, chromates or other metals such as
brass and chrome. Yes, you still must rinse.
6) Unload parts into a drying unit and dry completely at no greater than 120 degrees
F.
Quality Control
Proper and on-going training is extremely important to successfully barrel plating any
part. Records should be kept regarding all of the important parameters involved in
each step along the plating cycle. These should include things such as part
description, load size, voltage, time, thickness readings, chemical additions and any
problems which may have taken place during the cycle. All relevant data and notes
should be routinely reviewed to assure that the product will remain at a consistent
level of quality, can be repeated, and that the process can be continuously improved.
There are numerous quality systems which the customer may require the barrel
plater to employ such as the ISO 9000 standard which Merit has done. This will help
us to continue to achieve the highest level of customer satisfaction possible.
This information was reprinted and edited from Finishing.com and written by F. R. Zemo.
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