Definition - What does Anti-Pitting Agent mean?
An anti-pitting agent is a substance used when working with electrodeposits. This agent is used in addition to the electroplating solutions and it is meant to prevent the development of pores or pits on the surface of the electrodeposit.
Anti-pitting agents are often used in the case of multilayer systems since they can greatly improve the corrosion resistance of these systems, including thin magnetic films. There are different kinds of additives used as such agents because they are able to extract the hydrogen bubbles from the cathode, and thus can remove the pits.
An anti-pitting agent is also known as a wetting agent.
Corrosionpedia explains Anti-Pitting Agent
It is common for anti-pitting agents to be used together because they can have synergic effects. The hydrogen bubbles that are formed at the cathode can result in pitting if they are attached to the cathode's surface.
The main point of the anti-pitting agents is to decrease the tension on the surface of the cathode in order to promote the release of the bubbles. For such purposes it is common to use sodium lauryl sulphate.
Pitting can be the result of a wide array of causes:
- Interrupted current
- High iron concentration
- Organic impurities
- Low pH
- Incorrect anti-pitting agent concentration
If the surface of the cathode contains organic impurities, the anti-pitting agent will have to be improved and restored until it reaches the indicated concentration. Incorrect anti-pitting agent concentration can be solved by checking the tension on the surface of the cathode and increasing the concentration of the agent until it reaches the indicated levels.
An anti-pitting agent is a frequent addition to the nickel-iron coating that enhances the leveling power of the given electrolyte and it also improves the ductility of the coating. An anti-pitting agent of this kind could be a hydroxyethylatedoligoamide. Agents of this kind can be added to:
- Nickel sulfate
- Ferrous sulfate
- Nickel chloride
- Boric acid
- Sodium gluconate
- Sodium citrate
If an anti-pitting agent is used in plating baths for iron, there is no point in keeping ferric ions away from ferrous ion solutions, because the agent will make the electrodeposit smooth.