| 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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