GB1294205A - Rust inhibitor - Google Patents

Abstract

1294205 Rust-inhibiting composition "s a PRB" S A 11 Sept 1970 [27 Jan 1970 29 May 1970] 43605/70 Heading C7U A rust inhibitor comprises a tannic acid, a catalyst capable of initiating the chelation of iron atoms, and a cross-linking agent capable of linking two or more molecules of the resulting ferrotannic chelate. The tannic acid preferably has a molecular weight higher than 2000 and a hydroxyphenolic function number of 23 or more; it may be a pyrogallic tannin, a metapolygallic or gallic acid glucoside, an ellagic acid glucoside or a quinic ester of gallic or metapolygallic acid, and have a purity of 85-95% complete solubility in ethanol, and a viscosity of 150-200 cP at 50% by weight in ethanol at 25‹C. The catalyst may be an organic polycarboxylic acid which is saturated or unsaturated, hydroxylated or non- hydroxylated, aliphatic, alicyclic or aromatic, a polysulphonic acid or an amino acid, or an inorganic compound such as an electron acceptor or Lewis acid, e.g. Al 2 (SO 4 ) 3 , FeCl 3 or SnCl 4 . The cross-linking agent may be formaldehyde, a saturated or unsaturated aromatic or aliphatic dialdehyde, e.g. glyoxal, or an aliphatic or aromatic diamine such as hexamethylene diamine or paraphenylene diamine. The composition may contain organic solvents and water, preferred amounts of ingredients being (wt per cent) tannic acid 15-20, solvent boiling above 150‹C., 12-20, catalyst 3-15, cross-linking agent 3-15, volatile solvent 15-35 and water 15-40. The composition, when applied to a rusty surface forms a uniform layer of bluish black ferric chelate.