Method of retarding corrosion of metal surfaces in contact with boiler water systems which corrosion is caused by dissolved oxygen
AssigneeNalco Chemical Company
InventorsScott R. Harder, Cynthia A. Soderquist, Claudia C. Pierce
Life of this patent
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Abstract
New oxygen scavengers for boiler waters have been discovered, which oxygen scavengers are based upon N,N,N',N'-tetra substituted phenylenediamines. These compounds provide oxygen scavenging capabilities, metal passivating capabilities, volatility such that condensate systems in an operating boilder are protected, and may be formulated with other oxygen scavengers and other common treatment agents used in boiler waters. The preferred tetra substituted phenylenediamines are N,N,N', N'-tetramethyl-1,4-phenylenediamines, or its precursors.
Claims9
method of scavenging oxygen from boiler waters comprising treating said boiler waters with an effective amount of an oxygen scavenging compound, or mixtures of compounds, having the structure:
- ##STR7## ##STR8## wherein R, at each occurrence, is independently chosen from the group consisting of:
- (a) lower linear and branched alkyl groups having from 1-4 carbon atoms;
- (b) carboxylated groups having the structure:
- ##STR9## wherein n is from 1-3, and M is H, alkali metal cations, ammonium or amino cations or mixtures thereof;
- and
- (c) or mixtures of the above alkyl groups and carboxylated groups.
A method of scavenging oxygen from boiler waters comprising treating said boiler waters with an amine salt of an oxygen scavenging compound having the structure:
- ##STR10## wherein n ranges, independently at each occurrence, from 1-3, and wherein the amine salt is chosen from the group consisting of:
- (a) ammonium cation,
- (b) N.sup.(+) (H).sub.x (R').sub.y, wherein R' is an alkyl or alkoxyl group which may be linear or branched and which may contain from 1 to 20 carbon atoms and x and y both range from 0-4, provided the sum, x +y, is 4;
- (c) ##STR11## wherein R" is chosen independently, at each occurrence, from the group consisting of Hydrogen, lower alkyl groups having from 1-4 carbon atoms;
- and mixtures thereof.
- (d) ##STR12## wherein R' is as above, and z is from 1 to 3, and R'" is chosen from the group consisting of linear or branched alkylene groups having from 1 to 6 carbon atoms, ethoxy groups, propoxyl groups, and mixtures thereof;
- and
- (e) mixtures thereof.
A method of scavenging oxygen from boiler waters comprising treating said waters with an acid salt of an oxygen scavenging compound having the structure:
- ##STR13## wherein R is independently chosen at each occurrence from lower (C.sub.1 -C.sub.4) alkyl groups, and
- wherein the acid forming the acid salts is any acid from the group consisting of:
- (a) inorganic acids chosen from the group consisting of, hydroxamic acids, H.sub.3 PO.sub.4, H.sub.2 SO.sub.4, and mixtures thereof.
- (b) organic acids from the group consisting of formic acid, acetic acid, propionic acid, malic acid, maleic acid, citric acid, ethylene diamine tetraacetic acid, nitrilotriacetic acid, and mixtures thereof;
- (c) Nitrogen compounds containing at least one carboxylate functional group and having the structure:
- ##STR14## wherein R' is from the group consisting of methyl groups, ethyl groups and ##STR15## where n is from 1-3, providing at least one R' is ##STR16## and (d) amino acids, and
- (e) mixtures thereof.
Dependencies are inferred from the claim text.