Because it requires materials that are strong and can hold up over time, U.S. space agency NASA works on developing new high-tech materials to meet its needs. In one case, NASA scientists formulated a corrosion-resistant, zinc and potassium silicate (K2SiO3) coating to protect steel from the elements.
The single-coat coating was used on structures at the Kennedy Space Center on Florida’s east coast to protect its launch facilities from the salt-laden tropical environment, as well as the high temperatures and contaminants from the exhaust of rocket launches. The coating was used on other metal structures as well, such as bridges, ships, and even the Statue of Liberty.
This NASA-developed coating technology was licensed for use as a commercial product. Now manufactured by Polyset, the single-coat coating is used in marine environments on assets such as ships, offshore rigs, and dry docks; storage tanks; bridges; and pipelines.
Properties of the Coating
A 100% waterborne, high-ratio zinc silicate, the coating chemically bonds to steel, which prevents any undercutting if the coating is damaged. The chemical bond also allows the surface to be electrically conductive. The coating has high heat and abrasion resistance, contains no volatile organic compounds, and is self-curing with a drying time of 15 to 30 min at 77 °F (25 °C). The silicate chemistry is not affected by road salts or acid rain.
Unlike some other inorganic coatings that are applied in a single pass or sandblasted off, the NASA-inspired zinc silicate coating can bond to itself, so if the thickness of the first coat is too thin, it can be easily corrected. Although a thin coat is recommended (6 to 8 mils [152 to 203 µm] dry film thickness), over-application in some areas will not cause the coating to crack.
The coating was first developed in the 1970s. A NASA team at Goddard Space Flight Center was looking for a zinc anticorrosion coating that was easier and more cost-effective to use, so the chemists experimented with coating formulas and combined zinc powder and potassium silicate (K2SiO3) to protect metal surfaces from corrosion.
The end result was an effective and durable coating that chemically bonded with the underlying material to provide protection against sea spray, fog, and other corrosive elements. The protection continued even if the coating was scratched.
NASA licensed its patent to a company (Inorganic Coatings) so the coating could be sold in the private sector. Because the patents described the raw materials with very basic instructions, however, the company needed to refine the manufacturing process of liquid K2SiO3, a key component of the coating, before producing the coating commercially.
With the help of two chemical engineers at Polyset, Inorganic Coatings reworked the process until consistently good results were achieved. The two companies then signed an agreement calling for Polyset to provide the liquid K2SiO3 exclusively for the NASA-derived coating. Later, to save on costs, Inorganic Coatings tried unsuccessfully to produce the liquid K2SiO3 on its own. Because it was manufactured incorrectly, the coating turned back into a liquid when exposed to dew or rain.
When Inorganic Coatings stopped producing the zinc silicate coating, other companies began making the NASA coating with liquid K2SiO3 manufactured by Polyset. Whenever the anticorrosion coating delivered was not manufactured with Polyset’s liquid K2SiO3, the coating again turned into a liquid.
Due to the delivery of incorrectly manufactured batches and the advances made in other coating technologies at the time, the NASA-developed zinc silicate coating fell out of use.
The NASA formula, when manufactured correctly, is still one of the best product available to prevent corrosion of metals, according to Earl Ramlow, who started using the coating more than 20 years ago as an engineer working for a military contractor. In 2010, Polyset started marketing the coating directly to market under its own brand name, WB HRZS Single Coat System, and brought the coating back into use.