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Corrosion Inhibitor for Ethanolamines Plants

IP.com Disclosure Number: IPCOM000008614D
Publication Date: 2002-Jun-26
Document File: 1 page(s) / 20K

Publishing Venue

The IP.com Prior Art Database

Related People

W. C. Hoffman: AUTHOR

Abstract

It has been discovered that the addition of sodium borohydide to ethanolamine process streams is effective at preventing corrosion as well as color formation of metals.

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Corrosion Inhibitor for Ethanolamines Plants

Corrosion in amines plants has been a problem for decades. Even materials such as 304 and 316 stainless steels can corrode at unacceptably high rates in some amines processes. Therefore, a method for preventing this corrosion is needed.

It was found that ethanolamines process streams (i.e., unrefined mixtures of monoethanolamine, diethanolamine, and triethanolamine) became much less corrosive when sodium borohydride was added. In most cases, the corrosion was reduced by a factor of ten. For example, when ammonia column tails (crude ethanolamines) was heated at 180 °C for 48 hours with 304 and 316 SS corrosion coupons in a closed titanium Parr vessel, corrosion rates as high as 4-5 mils per year were observed. But when 2000 ppm by weight of sodium borohydride was added, the corrosion rates were always < 0.5 mpy.

Sodium borohydride treatment is effective in the presence of common impurities in the ethanolamines process, such as carbon dioxide, and even in partially aqueous streams. Metals that exhibit less corrosion with sodium borohydride include 304, 316, and 2205 stainless steels.

It is not known why the sodium borohydride is effective at preventing corrosion. Sodium borohydride also prevents color formation and this mechanism is understood to involve reduction of intermediate aldehydes.