Zinc chromate is a chemical compound used to protect metals from corrosion, developed by Ford in the 1920s. It is still used in the automotive and aerospace industries, but substitutes are preferred due to health risks. Zinc chromate primer is commonly used to protect galvanized metal or zinc-containing aluminum alloys. The color varies depending on pigments added during manufacturing. Zinc chromate is a carcinogenic compound, and OSHA regulates exposure limits and safety equipment requirements. Safer replacements include zinc and calcium phosphates.
Zinc chromate, which has the chemical formula ZnCrO4, is a chemical compound used to protect metals from corrosion. It was developed by the Ford Motor Company in the late 1920s as a primer coat. In 1936 it was used by the aircraft industry and the US military. While this coating is still in use, due to health risks and skin irritation, less toxic substances and other organic compounds are substituted whenever possible.
Commonly sprayed in the paint booth, zinc chromate primer is used to protect galvanized metal or zinc-containing aluminum alloys. It works by interacting with the metal surface when it gets wet. The primer begins to dissolve as moisture enters it and creates a shield, or passive layer, between the metal and the primer which prevents corrosion. Over time, the primer dissolves completely and the metal begins to corrode.
While the chemical composition of zinc chromate is important, there are no standards for the color. The natural color of the compound is greenish-yellow, but a variety of pigments are added during the manufacturing process to give it the color customers require. One of the most common colors is rusty red, used on automobiles. The aerospace industry commonly uses yellows and greens.
Since this compound is sensitive to light, it is mixed with black pigments to provide some UV resistance. The result is a green color. During the 1930s and 1940s, the primer was colored to indicate a second coat. Untinted or yellow primer meant a single coat, while a tinted primer would be one of the other colors.
Zinc chromate is one of a series of compounds known as hexavalent chromium. These chromium compounds are carcinogenic and long-term exposure has been shown to cause lung cancer. It is still used in the automotive and aerospace industries, but since 2000, less toxic substitutes have been used whenever possible.
In the United States, the Occupational Safety and Health Administration (OSHA) regulates exposure limits and safety equipment requirements. The OSHA personal exposure limit for zinc chromate is 0.1 milligram per cubic meter of air. OSHA requires workplace monitoring and medical surveillance of workers to protect them from exposure. Personal protective equipment is also needed to prevent exposure.
There are safer replacements for zinc chromate corrosion inhibitors. These include zinc and calcium phosphates. These compounds eliminate the dangers of chromates and still work well to prevent or delay corrosion.
Protect your devices with Threat Protection by NordVPN
