Sunday, November 6, 2011

Electro Cleaning Work

The purpose of this vital step is to remove surface contaminant of various types which would otherwise prevent proper adhesion of metal plating to the surface and/or cause the finish obtained by electroplating to lift oft completely.

The required mechanical surface preparation is needed such as machining, grinding, sanding and buffing, the metal may look perfectly clean but it isn't, to see the cleanness of metal should be chemically and microscopically clean.

The next step is electrocleaning where we make an apparently clean part even cleaner. Without this step, plating problem such as bare spots, poor or no adhesion, or even no deposit may develop.

The process electro-cleaning is simple enough, prepare one gallon container, mix 2 to 10 ounces of caustic soda or sodium hydroxide with one gallon of warm water. If you're operating from a pint sized stainless steel container, that's OK because the solution grows dirty in use and can be replenished from the handy pre-mixed plastic one gallon container of fresh solution.

Cathodic Cleansing of Tin, Brass, Aluminum, Magnesium, Nickel and Chrome
In this process, the part will be suspended in the above mentioned alkaline solution at room temperature, connected to the negative DC supply terminal. The positive DC terminal will be connected to the stainless steel container.

Increase DC current through the both until the part is gassing freely (generating hydrogen). Maintain this for one to two minutes. This bubble scrubbing action will also assist in the cleaning process.

The DC current will be in the range of 1 A to 1 Amp/sq.in. For an applied voltage of 3 to 1.2 VDC-not critical, just enough current to induce free gassing at the cathode connected workpiece. Exercises current will cause localized surface burning, so a little restrain is called for when cranking up the current to obtain the free gassing.

Ventilation to remove gas hydrogen that generated is mandatory because this stuff has a well earned reputation of going off with a bang (exploding) if given the chance to accumulation anywhere. One further note on safety concern the poisonous/corrosive nature of many of the nasty chemicals used. Also disconnected the DC supply at the power controller before making or breaking electrical contact at the working end. This will avoid sparking around the bath and the possible accidental ignition of the gasses generated.

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