Space program corrosion

Apart from being a constituent of rocket fuels, it is used to remove oxygen from boiler water to prevent the corrosion of the vessels. If, as some believe, hydrazine-based fuel cells eventually come into commercial use, demand will be enormous. Hydrazine hydrate production in noncommunist countries now stands at about 25000 metric tons per year, of which 17000 metric tons are used by the US with about 7000 metric tons taken by the space programs. 

In Europe, ADN is studied as an environmentally-friendly alternative to AP in space programs. When AP-based rockets are used, they produce enormous volumes of hydrogen chloride, which is harmful due to its acidic and corrosive character. Also other chlorine derivatives are formed which are toxic and are likely to contribute to the destruction of the... 

Most of NASA s anticorrosion efforts are concentrated on the launch site, where the high temperamres of the launch and the humid coastal atmosphere encourage corrosion. However, corrosion is a concern in other aspects of the space program, as well. Batteries used in the International Space Station (ISS) must be prevented from corroding in the ISS s artificial, earth-like atmosphere NASA s mission of planetary exploration requires that scientists know the corrosivity of a planet s atmosphere before a craft can land safely. Venus, for example, has a highly corrosive atmosphere that makes lander design very difficult. 

Nodal points of the platform require special attention for corrosion protection. Therefore the anodes have to be installed in the vicinity of these points, as indicated in Fig. 16-4. The spacing must be sufficiently large that the welded Joints of the nodes do not lie in the area of the lap Joints. The effort for calculating the optimal distribution with the lowest weight of anodes is considerable and has led to computer programs by which the anode distribution can be estimated [11]. 

In all space heating boiler systems there is a tendency to keep water treatment programs as simple as possible. Ideally, chemical inhibitors should be added in proportion to MU demands, metered water consumption, oxygen content, or other preemptive measurement. More typically, the standard process is to periodically (weekly to monthly) analyze the BW for a few basic control parameters, including measuring the multimetal corrosion inhibitor reserve, and then to merely top-up the inhibitor when the reserve is below the minimum specification. Chemical treatment often is added directly to the BW by hand-pump via a hose cock (bib cock) connection. 

A further longer term wet lay-up alternative is through the use of volatile corrosion inhibitors (VCIs) such as dicyclohexylamine acetate. These are dissolved in the water at a temperature below 60 °C, and the water is circulated for 4 to 5 hours. The boiler does not need to be completely filled because the VCI migrates to all parts of the boiler and reaches equilibrium in each of the void spaces. With traditional lay-up chemicals, the oxygen scavenger may become depleted easily (which is why the reserve usually is so high) and corrosion protection is quickly lost however, with VCI programs, there is always a volatile buffer available that maintains equilibrium and hence corrosion protection. 

Chemical treatment programs based on the direct addition of chemicals to FW or BW in order to prevent subsequent deposition, corrosion, or other problems from occurring. With precipitating types of internal treatments, the boiler waterside space is employed as a reaction vessel and, where a particular boiler design is unsuitable, inadvertent problems of fouling may occur. 

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