"Emaille de fer contre-oxide" is the name of an enamel which is said to protect iron pipes cheaply. The enamel is composed as follows: One hundred and thirty parts powdered crystal glass, 20.5 parts soda, 12 parts boracic acid. These substances mixed in the most careful manner are melted together in crucibles, the mass is chilled and transformed into a fine powder by crushing and grinding. The iron pipes and other objects of iron are first cleaned in the usual manner by corroding, dried and then coated with a very dilute gum arabic solution or any other gluing agent, and the powdered mass is spread over them by means of a sieve. The objects thus powdered are put in a room which is heated to 160° C. to drive out all moisture and are heated to dark redness, at which temperature the oxide coating melts.

Those processes, which produce a black protoxide layer on the iron by heating iron objects in supersaturated aqueous vapor, have not stood the test, as the layer formed will drop off or peel off after a short time, thus opening the way for rust after all.

The anti-rust composition called rubber oil is prepared as follows, according to the specification of the patent: The crude oil obtained by the dry distillation of brown oil, peat and other earthy substances are subjected to a further distillation. Thinly rolled India rubber, cut in narrow strips, is saturated with four times the bulk of the oil and left alone for a week or so. The mass thus composed is then subjected to the action of mineral sperm oil or a similar substance, until an entirely uniform clear substance has formed. This substance, which is applied on the metallic surfaces in as thin a layer as possible, forms a sort of film after slowly drying, which is perfectly proof against atmospheric influences.

The rust-preventive composition of Jones & Co., Sheffield, is a composition of wax, fat, turpentine, and small quantities of iron oxide.

According to a process patented by A. Buchner in Germany, the iron objects are first painted with a mixture of an alkaline glue solution and rosin soap. The alkaline mass enters all the pores and fissures and prevents the rust from extending under the coating. After the first coat is dry a second one is applied of the following composition: Five parts linseed oil boiled with peroxide of manganese; 2.25 parts turpentine; 0.25 parts benzol; 20 parts zinc dust, carbonate of calcium, lead oxide, or peroxide of manganese. The mixing of the liquid with the powders must be done immediately before use, as the mass solidifies after 10 hours, and is then no longer of working consistency. The second coating, which should only be thin, hardens quickly. The paint is weatherproof, does not peel off or blister, and adheres so firmly that it can only be removed with mechanical means.

A patented process to prevent rusting of wrought or cast iron consists in applying with a brush a strong solution of potassium dichromate and drying in a stove or over an open fire. Drying at ordinary temperature is not sufficient. To ascertain if the heat is strong enough the iron is moistened with a little water. So long as this takes up any color the heat must be increased. When the proper degree of heat is reached a fine deep black layer results, which is not acted upon by water, and protects the surface from the action of the atmosphere. A permanent lustrous rust preventive is secured as follows: The well-cleaned iron parts are suspended for a few minutes in a blue vitriol solution, so that a delicate skin of copper forms on the surface; if the pieces rinsed off with water are then moved about for a few minutes in a solution of sodium hyposulphite faintly acidulated with hydrochloric acid, they assume a blue-black coating of copper sulphide, which is equally permanent in air and in water. The black surface may be immediately rinsed with water, dried with a rag or blotting paper, and polished at once. It possesses a steel-blue luster, adheres well to the iron, will stand treatment with the scratch brush, and protects against rust in a most satisfactory manner.