Patent GB-473991-A (GB)
Title: Improvements in or relating to the cleaning and pickling of metals
IPC: C23G1/06
Filed: 1936-04-24
Abstract: Metals are cleaned and pickled in an acid bath containing as inhibitor a resin produced by reacting an unsaturated aldehyde such as crotonaldehyde and ammonium sulphide.  Other suitable aldehydes include ethyl hexenal or aldehydes converted to unsaturated aldehydes under reaction conditions, such as acetaldehyde or aldol.  A substance containing a halogen ion, such as sodium potassium or ferric chlorides, potassium bromide or potassium iodide, may be added to the bath, and the resin may, if desired, be treated with concentrated sulphuric or hydrochloric acid.  The resins may be introduced into the bath as solutions in, for example, acetone, alcohol, or ethylene glycol or as dispersions dispersed by sulphite cellulose waste, saponin or gum arabic.  In examples: (1) crotonaldehyde is condensed with aqueous ammonium sulphide in the presence of ice and the product used, with or without the addition of sodium chloride, in a sulphuric acid pickling bath; (2) the condensation product of example 1 was heated with sulphuric acid and then used in a pickling bath, dried by treatment with solid sodium chloride and lime or treated with gaseous ammonia or salt-forming alkali; (3) the condensation product of example 1 was treated with hydrochloric acid and used in a pickling bath or dried.  The Specification as open to inspection under Sect. 91 refers in general to the manufacture of condensation products of aldehydes and quaternary ammonium sulphides (that is ammonium and substituted ammonium sulphides) and the use thereof as inhibitors.  Salts, particularly those that react acid or alkaline in aqueous solution, catalyse the reaction.  Substituted ammonium sulphides include alkyl-or aryl-, ethyl-, diethyl-, triethyl-, ethanol-, diethanol- and triethanolammonium sulphide, pyridinium sulphide, piperidinium sulphide, quinolinium sulphide.  An example refers to the condensation of crotonaldehyde and ethanolammonium sulphide.  This subject-matter does not appear in the Specification as accepted.ALSO:Metals are cleaned in an acid bath containing as inhibitor a condensation product of an unsaturated aldehyde and ammonium sulphide.  Suitable aldehydes include croton aldehyde, ethyl hexenol or aldehydes converted into unsaturated aldehydes under reaction conditions such as acetaldehyde or aldol.  The condensation product may be treated with concentrated sulphuric or hydrochloric acid.  Substances containing a halogen radical such as sodium, potassium or ferric chlorides, potassium bromide or potassium iodide may be added to the bath.  The condensation products may be introduced into the bath as solutions in, for example, acetone, alcohol, or ethylene glycol or as dispersions using as dispersing agent sulphite cellulose waste, saponin or gum arabic.  The Specification as open to inspection under Sect. 91 refers to the use of condensation product of aldehydes and quaternary ammonium sulphides (that is ammonium and substituted ammonium sulphides) as inhibitors.  Suitable substituted sulphides include alkyl-, aryl-, ethyl-, diethyl-, triethyl-, ethanol-, diethanol-, and triethanol-ammonium sulphides, pyridinium, piperidinium and quinolinium sulphides.  This subject-matter does not appear in the Specification as accepted.