The Solubility of Metals in Acids Containing Formaldehyde

Organic Inhibitors of Corrosion

“…Of the oxygen-containing inhibitors there are the alde-hydes5' 6,12,14,15 with formaldehyde being quite common, various 116 CHARLES A. On examination it is found that each one of these inhibitors is or contains a compound or compounds which have in their structure one or 'more atoms of the elements that occur in groups 5 and 6 of the periodic table of the elements, all of which can form onium compounds.…”

Organic Inhibitors of Corrosion, Aliphatic Amines

“…It is easy to understand that the ammonium ion will not have a large cross-sectional area taken parallel to the surface of the iron, and therefore will not be a very effective inhibitor. If one of the hydrogens is replaced with a long normal hydrocarbon chain containing 16 carbon atoms and the chain stands perpendicular to the metal surface (as Langmuir has shown to be the case with fatty acids when a monomolecular layer is spread on water), the cross-sectional area of this amine parallel to the metal surface will not be very great-in fact, 20.5 square Á. Many molecules of such an amine will be required to make a complete monomolecular layer, and these must be packed closely together like so many matches on end to cover the whole surface of the metal and thus form a continuous protecting layer.…”

“…If the long hydrocarbon chain is somewhat inclined to the metal surface, the projected area of the chain on the surface of the metal will be considerably greater than is the case when the chain is perpendicular to it. If the chain lies in the surface of the metal, the amount covered will be very greatnamely, y/20.5 X 24.2 square Á., since such a chain of 16 carbon atoms is 24.2 Á. in length. When a second and a third aliphatic group replace the hydrogens of ammonia to form amines and these chains are inclined to the metal surface, a greater area is covered, particularly with increasing length of chain.…”

“…One patent (7A) in 1919 covers the use of crude anthracene and oil residues, and another in 1920 (17) pertains to the use of extract of sumac for pickling baths. The use of aldehydes (6,7,13,16,18), organic bases (10,19,22,23,26,27,32), and organic compounds containing nitrogen, arsenic, phosphorus, sulfur, selenium, and other complex synthetic or natural organic substances and by-products (2, 5,8,11,12,25,29,30,31, and some seventy United States, British, and German patents) have been proposed as inhibitors or have been investigated.…”