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Overview

Plating is the application of a metallic layer to a base layer. There are several application methods including but not limited to:

  1. Fusing one metal onto another metal surface
  2. Spraying a metallic coating
  3. Electroplating a metallic coating

Electroplating is the process of applying a metal coating to a part immersed in an electrolytic solution through an applied or induced electric current. Metal coatings may include Cadmium, Chromium, Cobalt, Copper, Gold, Indium, Iron, Lead, Nickel, Platinum, Silver, Tin, Zinc, Brass, and Bronze.

Plating is widely used in industries such as automotive, avionics, aeronautics, electronics, jewelry, and toys. The coating produced is usually for decorative and/or protective purposes or enhancing specific properties of the surface.

There are many types of pollutant emissions resulting from plating processes. For example, Hexavalent Chromium electroplating causes the formation of hydrogen gas at the cathode. The gas rises to the surface of the plating bath causing the formation of a chromic acid mist which is a hazardous air pollutant.

Electroplating wastewater can contain highly toxic cyanide, cyanide complexes and metal ions that makes treatment a complex problem. Additionally, several hazardous wastes are commonly generated by the electroplating industry. Cyanide- and acid-based solutions, and materials such as plating bath filters and resins, all have the potential to cause injury and harm to our environment if not disposed of properly.

Based in part on the Pollution Prevention Research and Implementation project for Michigan Metal Finishers, Zinc/Nickel electroplating is considered a replacement for Cadmium electroplating for many applications, including automotive. Cadmium electroplating is still the preferred method for aerospace and the Department of Defense.

Some other Best Management Practices are recommended to help reduce the quantity of hazardous waste generated and the quantity of wastewater discharged to a POTW (Publicly Owned Treatment Works) which will reduce costs for businesses.

Benefits Include:

  • Saving money on waste management costs.
  • Reducing concerns about penalties and liability.
  • Creating a safer, healthier workplace.
  • Promoting positive public relations with clients, customers, and the local community.

First Steps:

  • Make a commitment to reducing wastes in every area of your business.
  • Evaluate your facility’s wastes and identify areas where changes can be made.
  • Encourage the participation of all employees through education, training and incentives.

Cleaning and Surface Preparation:

  • Use abrasives instead of aqueous cleaners or solvents.
  • Use non-chelated cleaning chemicals and mild chelators.
  • Reuse or recycle cleaning agents.
  • Reuse or recycle rinse water.
  • Use countercurrent or cascade cleaning systems.

Reduce Dragout:

  • Allow for drain time over the bath. An additional 2 to 3 seconds of drain time can reduce dragout by 50 percent.
  • Install spray rinses. Rinsing conducted over heated baths washes dragout directly into the plating bath and uses a minimal amount of water.
  • Position parts to keep dragout at a minimum. Tilt parts so that liquid drains freely as the parts are removed from the baths. Orient parts so that the smallest surface area is in contact with the solution as a part is removed.
  • Install drain boards between process and rinse tanks.
  • More information, including videos on dragout reduction, is provided by the Surface Technology Environmental Resource Center (STERC).

Reduce Water Use:

  • Use conductivity control systems, which can reduce water use and wastewater generation. Conductivity control systems monitor rinse water conductivity to maintain adequate chemical concentrations and reduce water use by adding rinse water to rinse tanks only when necessary.
  • Use low-cost flow restrictors or solenoid valves and timers to reduce water use and wastewater generation. Solenoid valves can be installed with spring-wound timers on rinse water lines to control flow to each of the rinse tanks.
  • Use counter-current rinsing to reduce water use and wastewater generation.
  • More information, including videos on water use reduction and wastewater generation, is provided buy the Surface Technology Environmental Resource Center (STERC).

Extend Bath Life:

  • Improve bath purity by using deionized water for bath makeup and filtering the bath continuously.
  • Maintain each bath by measuring its pH, temperature, and concentration daily. Add chemicals only when needed.
  • Use bath additives, which can replenish process chemicals and add chemical agents to boost bath performance.
  • Remove impurities in the process tank through membrane filters, ultrafiltration, and ion exchange.

More specific information regarding Chromium Electroplating Operations and Plating and Polishing Operations is available.

The topic of Environmental compliance in the plating industry [ZIP] was presented during an Indiana Chapter meeting of the National Association for Surface Finishing (NASF) on September 15, 2015.

CTAP is available to assist Indiana’s businesses engaged in stationary engines. Contact CTAP using the CTAP Partner Portal to request help. It will require setting up a free account through Access Indiana.

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