The Effects of Muriatic Acid on Anodized Aluminum

Anodizing is a treatment applied to safeguard aluminum alloys from corrosion. Anodized aluminum is second only to diamond as the hardest known substance; it is commonly used as raw material in aviation, automotive and aerospace manufacturing. The method for anodizing aluminum utilizes aqueous sulfuric acid -- due to its low pH -- which improves its resistance to corrosion. Muriatic acid is a strong electrolyte, but it is not recommended as an alternative option to yield anodized aluminum.

Anodizing Process

• Anodizing occurs via an electrolytic process that involves coating aluminum metal with an oxide layer under acidic conditions using an electric current. The electrolyte is chosen according to its alkaline, conductive and permeable characteristics. Aluminum metal serves as the anode and is oxidized to form aluminum oxide or anodized aluminum. The properties of anodized aluminum are dependent on additional electrolysis conditions including electrolyte temperature, anodizing duration and voltage used.

Properties of Anodized Aluminum

• Anodized aluminum is the most widely used non-ferrous alloy. It has a very hard surface, which accounts for its use in air and space vehicles. Despite its durability, it has a low density, making it useful for containers and other packaging. It is strongly resistant to corrosion from the atmosphere and in solution. Anodized aluminum also has high electrical and thermal conductivities.

Muriatic Acid

• Muriatic acid is the historical name for hydrochloric acid. It is a strong, corrosive acid and has widespread industrial applications; approximately 20 million metric tons are produced each year. Muriatic acid dissociates fully in water into hydrogen and chloride ions. It is commonly used to prepare samples for chemical analysis and as an acid catalyst for chemical reactions.

Muriatic Acid on Anodized Aluminum

• The type of electrolyte used in the anodizing process affects the final properties such as corrosion rate, adhesion, adsorption, surface hardness and conductivity of the anodized aluminum . Muriatic acid is not used as an electrolyte in aluminum anodizing as it reacts with aluminum, dissolving it to form metal chlorides and hydrogen gas.