Hull Cell Analysis

A hull cell is a testing tool, or a miniature electroplating cell, in which an electroplating solution is evaluated across the range of operating conditions. An evaluation of the deposit on the cathode across a range of current densities is useful in demonstrating the capabilities of a plating bath solution.

This video will show you how to run a hull cell.

Transcript of Video:

Here are the materials you’ll need:

1. The hull cell test or analysis is designed to analyze the deposit appearance and deposit characteristics of a specific electroplating solution. Hull cells may come in a variety of sizes, but the 267 milliliter is the most common.

2. A hull cell anode: this needs to correspond to the plating bath to be evaluated. There is a specific anode required for each plating process. Today we are evaluating an acid zinc solution so we will be using a zinc anode.

3. Obviously we need a plating solution: as we previously mentioned we are using  acid zinc electroplating solution.

4. A laboratory grade DC Power source/rectifier with variable control in necessary some laboratory units have control for both amperage and voltage. This unit is a single source control for voltage. A rectifier that has DC voltage output of 0 to 10 Volts and amperage output of 0 to 10 amps is preferred.

5. Appropriate Clamps and leads are also necessary. Here color coded cables to connect the rectifier to the hull cell. Alligator clips are easy connections from the rectifier to the anode and the cathode.

6. The cathode or hull cell panel is typically zinc coated steel. In our evaluation we will be using a zinc coated steel panel.

7. In the case of the zinc coated panel, the zinc is there to protect the panel from rusting and excess scratching. To remove this protective coating a 50 percent solution of hydrochloric acid is used to strip the zinc coating prior to plating.

8. Safety first. It is important to wear the proper personal protective equipment. This should include gloves, goggles and a lab coat. You’ll also need to keep a pair of lab tongs handy. If you have any safety questions, check with your company’s safety officer.

9. Some processes require agitation others do not: when solution movement or agitation is required either air or mechanical agitation is used. Here, we’re using an aquarium air pump to supply air agitation.

10. You will need a timer. Here we have a lab grade timer but even a simple stop watch or even kitchen timer will suffice.

11. And finally, a hull cell ruler to interpret the results.

The Procedure:

Now that we have all the necessary equipment we are ready to get started. Again, we will be running an acid zinc hull cell. It will be processed at 2 amps for 5 minutes at ambient temperature with air agitation.

1.  Put on your safety equipment.

2.  Place the anode in the hull cell: to reiterate, this is an acid zinc process so we will use a zinc anode.

3.  Prepare the solution and note and document the following:

  • temperature, which is ambient
  • plating time: 5 minutes
  • amperage: 2 amps
  • agitation: air

4. Add the plating solution to the hull cell.

5. Fill to the line to 267 ML: this is critical to achieve accurate interpretation of the results.

6. Begin agitation of the solution: once again we are using an aquarium pump.

7. Now prepare the cathode or hull cell panel.

For the zinc hull cell we are using a zinc coated panel. Wear rubber gloves and use lab tongs for safe handling and to prevent contaminating the panel. Immerse the zinc plated steel panel in a solution of 50 percent by volume hydrochloric acid to strip off the zinc plating. Place the panel under cool water and wipe the surface with a wet cotton cloth or wet paper towel to ensure cleanliness. This will remove small particles from the surface that can interfere with the evaluation of the deposit on the cathode. Rinse again with cold water to ensure a clean surface until you see a water break free surface.

8.  Place the panel in the hull cell and connect the electrical connections (the clamps and leads) corresponding to the correct polarity: positive to the anode, negative to the cathode or panel.

9.  Set the timer to the correct time, in this case we have chosen 5 minutes.

10.  Turn on the rectifier or power source.

11.  Adjust the amperage to the desired level, here we have chosen 2 amps.

12. Start the timer, again here we have chosen 5 minutes.

13.  Once the timer ends, turn off the power.

14.  Disconnect the cathode/panel and remove it with tongs.

15.  Once the panel is removed rinse it in cool water.

  •  In the case of a zinc-plated panel, it’s a good practice to take the panel through a bright dip process before analyzing it
  • With tongs, dip the panel into a 0.25-50% by volume solution of nitric acid for 3-5 seconds
  • Rinse with warm water
  • Dry with forced air or an absorbent towel

Now the panel is ready for analysis.