Space: the final frontier — for corrosion engineering. Keeping individuals alive and functional on board the International Space Station (ISS) requires an incredibly complex system of life-support machinery and equipment monitoring.

The fragility of life in space, where minor failures can turn catastrophic in an instant, has propelled the science and astronautical community to seek resolutions for the effects of the hazardous circumstances astronauts face.

Although the weather outside tends to be around minus-250 degrees F, one of the biggest problems aboard the ISS is keeping everyone and everything cool. This is the primary job of the Internal Active Thermal Control System (IATCS).

On the ISS, both bodies and equipment generate a great deal of heat in the enclosed space. Without air to distribute heat around the ISS by conduction or convection, heat tends to stay wherever it happens to be, creating a situation that would quickly become intolerable for the astronauts and would certainly cause failures in the sensitive instruments.

In addition to the heat generated by internal conditions, the sun is uncooperative. Heating and cooling in space are primarily caused by radiation. Facing the sun, the ISS can heat up by 500 degrees from the frozen chill of the dark side.

To level out temperatures and keep equipment running smoothly, the IATCS acts as a heat sink. It operates using a water-based fluid — and where there is water, there will be corrosion.

In this case, NASA found a unique challenge in two different types of corrosion: precipitates on metal surfaces and microbiologically-influenced corrosion (MIC). Initially, the fluid mixed water with phosphate to control corrosion, with borate to act as a pH buffer, and with silver sulfate to counter the effects of microbial incursions.

The fluid changed over time, though. Carbon dioxide diffused through the hoses, causing the pH levels to drop. Nickel and silver began to deposit on metal surfaces, and phosphate precipitated into nickel phosphate. Essentially, the microbial controls failed, and colonies began to multiply at an alarming rate within the equipment.

The weakest points of the entire IATCS system are the extremely thin loops made of nickel. Silver deposits were starting to pit and corrode these loops, threatening the heat exchangers. Biofilm from microbial growth was beginning to compromise the material as well, amplifying the material damage from the pitting.

NASA decided to use ortho-phthalaldehyde (OPA), based on its effectiveness at low concentrations, low toxicity and compatibility with other environmental control and life-support systems (ECLSS). The problem then became how to apply it in a working station without taking down the IATCS.

The solution was the creation of a resin to safely introduce OPA into the IATCS while keeping all systems operational and limiting exposure to the crew. This also inferred the necessity of a second resin for removal in case of degradation or leak.

Since 2007, OPA has been working hard to fight microbes in outer space to let cooler heads prevail on board our planet's only home away from home.