Crystals, Hydrogen Embrittlement and Filtration
Electrodeposited metal is formed by aggregation of crystals. Cast metals have a much larger crystalline structure than do the cold applied electroplated metals. In electroplating, the initial layers of the deposited metal will assume the grain of the base metal. Continued electroplating will cause the deposited metal to assume its normal crystalline shape. The deposit is said to be “crystalline” when the crystal structure of the plate is visible to the naked eye. The deposit is said to be “finely crystalline” where the crystallic structure can only be observed under a microscope. In order to achieve a smooth bright finish, the finely crystalline structure must be achieved. Additive agents improve the brightness of the plate by helping to produce a finely crystalline structure. Nickel brighteners are one such example. usually, electroplated metals have a satin appearance and either additives or buffing must be employed to achieve a bright appearance.
Hydrogen given off at the cathode can cause hydrogen embrittlement of the base metal and the deposit. This can cause the base metal or deposit to become brittle and crack under stress. The embrittlement may be overcome in the plating process by heat treatment, which drives off entrapped hydrogen. This is widely used for hard chromium plating. For decorative plating, embrittlement should not best a problem unless the workpiece is given excessive treatment in the pickling vat. The workpiece should be prepared and treated such that excessive cleaning and pickling are not used. Steels that have been hard chromium plated can be relieved of the entrapped hydrogen by heating to 375 degrees for three hours or more. Under the microscope, chromium will be seen to have a cracked surface which is permeable to the hydrogen and will allow it to escape when heated as described.
Impurities in the plating baths must be removed to prevent spoiling of the final finished surface. The solution is pumped from the tank through a filter of activated carbon or other materials and then pumped back into the tank. Filtration generally involves two processes. Organic impurities are removed by an activated carbon treatment and solid impurities are removed by passing the solution through filters. The pumps and filters used are constructed and coated with corrosion resistant materials, i.e., polypropylene. Some metallic impurities are removed by addition of chemicals that cause the impurities to precipitate out of solution or to be filtered out, and/or by using what is known as a dummying process. Both of these processes will be covered in subsequent sections of this manual. Activated carbon should never be used in the chromic acid vat. Chromic acid is normally not filtered. The best advice is to work with your supplier (see supplier’s list) for your particular application. He will be able to advise you of the correct type of filtration for a given bath.
TITLE: HOBBYIST ELECTROPLATING MADE EASY- 3 day special! Get paperback or save money and
time with an instant download!
For paperback, click on this Paypal button:($11)
for instant download click on this button:($6)
AUTHOR: RANDELL L.NYBORG
LIST PRICE: $8.00 + $3.00 s/h for paperback, or $6.00 FOR INSTANT DOWNLOAD AND NO S/H!
This is a 70 page book It teaches the process of plating chrome, nickel, and gold
on small objects, using homemade equipment that will only cost a few dollars. It has hard
to find plating bath formulas. Describes metal preparation for plating. It does not
assume prior knowledge and the entire electroplating process is demonstrated so anyone can
follow and understand. Also gives formulas for plating zinc, brass, silver, copper,
and protective coatings, in addition to chrome, nickel, and gold. Thousands sold. Learn
this process and go into business for yourself.
PLATING KIT---Hobbyist Electroplating book from above, + 2 Dry oz. Nickel Powder
+ Anode! Only $20.00 + Priority shipping ($5.50)
Our best selling plating book,described above, plus now, get plating right away! With the book, you
get 2+ ounces nickel plating chemicals,dry weight, plus a nickel anode, 99% pure nickel!We
give you the stuff that is hard to find or expensive at a very affordable price, and you
can plate items immediately, or use it as an instructional kit to see if you want to take
plating further. You can supply the battery and wires/clips yourself and save lots of
money! Add warm, distilled water to the nickel chemical, and you are ready to plate! Why
buy the liquid solution from others that is mostly water? We tell you what is in it!
Quick instructions included, or read the book first. Cheapest price for
instructions/chemicals anywhere in the world!
The vat in the photo is for demo purposes only and does not come with the kit. Get your
own vats at Wal Mart.