Chicken Feather-Derived Keratin-Based Bioplastic as a Corrosion Inhibitor for Mild Steel in 0.1 M HCl: Electrochemical, Gravimetric and Adsorption Studies

Rust is a slow, relentless thief that steals value from the world's metal infrastructure. When steel is exposed to acidic environments, such as those found in industrial cleaning or chemical processing, the metal dissolves rapidly, shortening the life of pipes, tanks, and machinery. To stop this, engineers often add chemical inhibitors to the acid. These are substances that coat the metal surface, creating a barrier that slows down the chemical reaction eating the steel away. For decades, many of these inhibitors have been synthetic organic compounds. However, there is a growing interest in finding solutions that are not only effective but also derived from renewable sources, turning waste into a protective resource. This shift is driven by a desire to reduce reliance on petrochemicals and to find new uses for materials that would otherwise be discarded.

In a recent study, researchers explored a unique source for such a protective agent: chicken feathers. These feathers, which are a massive byproduct of the poultry industry, are rich in a tough protein called keratin. Keratin is the same structural material found in human hair and fingernails. The researchers asked a simple question: could they transform this waste material into a bioplastic film that, when dissolved in acid, would stick to steel and stop it from rusting? They did not just look at the feathers as a raw material; they processed them into a specific composite film mixed with glycerol and cellulose, then tested how well this mixture protected mild steel in a solution of hydrochloric acid.

The team began by collecting waste feathers from a processing plant in Nigeria. They cleaned the feathers thoroughly, removing dirt and oils, and then broke them down using a chemical process to extract the keratin protein. This extracted protein was then mixed with glycerol, which acts as a softening agent, and microcrystalline cellulose, a plant-based fiber, to create a flexible film. This film was the "bioplastic" they intended to use. Before testing its protective powers, the researchers examined the material closely using various scientific tools. They used infrared spectroscopy to confirm the presence of protein structures, electron microscopy to see the surface texture, and thermal analysis to understand how the material behaved under heat. The results showed that the material retained the key chemical features of the original protein, even after being turned into a film.

To test the material's effectiveness, the researchers placed small pieces of mild steel into a bath of hydrochloric acid. They ran these tests at different temperatures, ranging from a mild 30 degrees Celsius up to a hotter 60 degrees Celsius. In some tests, they added nothing to the acid, serving as a control to see how fast the steel would rust on its own. In other tests, they added the keratin-based bioplastic at varying concentrations, up to 0.8 grams per liter. They measured the corrosion in two main ways. First, they weighed the steel pieces before and after soaking them in the acid to see exactly how much metal had been lost. Second, they used an electrochemical method, which measures the flow of electrical current caused by the corrosion reaction, to get a precise reading of how fast the metal was dissolving at any given moment.

The results showed that the chicken feather material did indeed slow down the corrosion. As the concentration of the bioplastic in the acid increased, the rate at which the steel dissolved decreased. At the highest concentration tested, the material reduced the corrosion rate significantly. However, the protection was not perfect, and its performance changed with temperature. At the lowest temperature tested, the material reduced the corrosion rate from 37.56 millimeters per year to 21.79 millimeters per year, representing an inhibition efficiency of about 42 percent. As the temperature rose to 50 degrees Celsius, the material became even more effective, reaching a peak efficiency of 54 percent. But when the temperature climbed further to 60 degrees Celsius, the protection dropped, falling back to about 32 percent. This suggests that while the material works well, the heat eventually causes it to become less stable or less effective at sticking to the metal.

The researchers also looked at how the material interacted with the steel surface. By analyzing the data, they found that the bioplastic acted as a "mixed-type" inhibitor. This means it slowed down both the chemical reactions that release electrons from the metal and the reactions that consume them, rather than blocking just one side of the process. The data fit a mathematical model known as the Langmuir model better than other models, which suggests that the molecules of the bioplastic spread out across the steel surface in a single layer, covering the spots where rust would normally start. However, the authors were careful to note that because the bioplastic is a complex mixture of different proteins and fibers, not a single pure chemical, this model is an approximation. It describes the behavior well, but it does not prove exactly how every single molecule is arranged on the surface.

The study concluded that converting waste chicken feathers into a bioplastic is a viable way to create a corrosion inhibitor. The material successfully reduced the corrosion of mild steel in acidic conditions, proving that poultry waste can be transformed into a functional industrial product. The researchers emphasized that while the results are promising, the material is not a miracle cure. Its effectiveness depends heavily on the concentration used and the temperature of the environment. At higher temperatures, the protection weakens, indicating that the material might not be suitable for very hot industrial processes without further modification. The work stands as a demonstration of a practical method to turn a common waste product into a useful tool for protecting metal, offering a glimpse into how biological materials might one day replace synthetic chemicals in industrial applications.