Chrome Plating is not as simple as 'just dipping it' in the solution. It is actually very complex, as you can see from the picture. Learning how to do this properly takes years. However, it is very interesting, and the journey from Apprentice to Platers Helper to HCP status is quite rewarding.
The process of electrolysis accomplishes chromium plating. Utilizing DC current at a specified voltage and amperage, you have a Cathode, which is negative (the part to be plated) and an Anode, which is Positive. The Cathode is placed at a predetermined distance from the anode in the electrolyte (the solution), and the current is applied. The amount of time the Cathode (part) is left in this condition will determine the thickness.
Various different types of masking are utilized to stop off on areas that do not require plating—tapes, plugs, shields, special lacquers, etc. A good plater knows what to use, and they will probably not tell you what or where, so just tell them what you do not want to be plated. Or just tell them what is to be plated. They will figure out the rest. If not, they will contact you for clarification.
So now, lets Chrome Plate something: After a part arrives in the plating plant, it goes through Incoming Inspection. Verifying count, condition of material, and figuring out where and how much plating is to be applied are some of the areas covered.
Once this is determined, it will be masked off for abrasive blasting to ensure the area to be plated is very, very clean. After blasting, the area is kept protected so as not to form any oxides on the surface. It must not be touched by anything from this point onward.
The part is then masked and racked for plating. Very expensive tapes (some costing as much as $50 a roll at this writing), lacquers, shields, plugs, etc. are used. Knowing what and where to apply takes years of knowledge to master.
After masking an electrode (anode - Positive in the tank, remember?) has to found or fabricated to conform to the configuration of what you are plating. This is also a crucial step in the process and requires years of knowledge to fabricate properly.
The part must now be 'racked' for introduction into the plating bath. Again, this takes years to learn properly in order to obtain the desired results.
The efficient accomplishment of all these tasks is imperative in order to make a profit on what you are doing.
We are now ready to place the part in the plating solution. In-Process Inspection is required at this time. The Plating Bath 'make up' (ingredients) are verified, as well as temperature, voltage, amperage, and anode to cathode spacing. All electrical contacts are cleaned to ensure proper transfer of current. Knowing how all these things are adjusted also takes years to learn.
The part is now 'reverse current' etched for final cleaning and activation of the surface. This ensures proper adhesion in that you not only have a mechanical bond but a molecular bond as well. Knowing how long and at what current valuation is critical.
After proper 'reverse' the part is placed in plating position, and the actual plating commences. The proper voltage and amperage is adjusted on the DC power supply.
The plating 'rate' is now determined, and the part is allowed to remain in the solution for the proper duration to obtain the required 'build-up' of Chromium. Plating rates are very slow for Hard Chrome plating, generally, in the neighborhood of .001" per hour.
Now you have some idea as to why it takes so long for you to get your parts back from your plater?
The part must be attended to during the plating process. 'Trees', solution level, and monitoring of all values previously mentioned are very important. One small detail left unattended, and you will have to strip the part and start all over again. (This is one reason it is difficult for your plater to give you a delivery date...things sometimes do go wrong, and the delivery date has to be pushed back due to reprocessing.)
After plating, the part must be unracked, checked, the masking removed, and then rinsed and cleaned. This also can take considerable time, as the 'masks' are very durable, being able to withstand an acid solution at high temperature. They sometimes must endure plating cycles of 48 hours or more for heavy build-ups.
After cleaning, Final Inspection is made to verify plating thickness, visual on the chrome and part condition, proper cleaning, etc.