Rust removal and composition thereof
AssigneeDearborn Chemical Company
InventorsJohn E. Waller, John A. Gray, David A. Aston
Life of this patent
Estimating the term…
Abstract
Iron oxide deposits are removed from substrates by use of aqueous solution at approximately neutral pH containing a phosphonate (e.g., hydroxyethylidene diphosphonic acid), a reducing agent (e.g., sodium sulfite), and a corrosion inhibitor (e.g., benzotriazole). Optionally, a surfactant and dispersant may be included.
Claims18
A method of removing iron oxide from a metal substrate which includes a surface of iron or steel comprising treating the substrate with an aqueous use solution containing from about 0.09 to 2.2 weight percent of the phosphonate hydroxyethylidene diphosphonic acid, from about 0.015 to 0.4 weight percent of a reducing agent, and from about 0.0015 to 0.04 weight percent of a corrosion inhibitor selected from the group consisting of benzotriazole, tolyltriazole and their alkali metal salts.
An improved aqueous dispersant composition, wherein the improvement comprises a descalant concentrate in which the actives consist essentially of, in weight % of the composition, the phosphonate hydroxyethylidene diphosphonic acid, about 3-11;
- a reducing agent, about 0.5-2.0;
- a corrosion inhibitor selected from the group consisting of benzotriazole, tolyltriazole and their alkali metal salts, about 0.05-0.20;
- and optionally up to about 5 weight percent of a carboxylated amphoteric surfactant;
- and wherein the dispersant is at most, about 8 weight percent of the composition.
An improved dispersant composition, wherein the improvement comprises a descalant formulation consisting essentially of dry basis actives, in weight % of the composition:
- Hydroxyethylidene diphosphonic acid, about 40.2;
- sodium sulfite, about 6.3;
- benzotriazole, about 0.6;
- carboxylated amphoteric surfactant derived from mixed caprylic and hexoic acids, about 5.7;
- and NaOH, about 30.0.
An aqueous descalant composition comprising:
- (a) from about 0.09 to all weight percent hydroxyethylidene diphosphonic acid;
- (b) from about 0.015 to 12 weight percent of a reducing agent selected from the group consisting of sodium sulfite, isoascorbic acid, diethylhydroxylamine, glucose and hydrazine;
- and
- (c) from about 0.0015 to 0.2 weight percent of a corrosion inhibitor selected from the group consisting of benzotriazole, tolyltriazole and their alkali metal salts;
- the weight ratio of said components (a), (b) and (c) in said composition being about 3 to 11 parts component (a):
- 0.5 to 2 parts component (b):
- 0.05 to 0.2 parts component (c).
Dependencies are inferred from the claim text.