The MetaLayeR, as the instrument is known, has proved commercially serviceable as a means of applying protective metal coatings upon substances subject to corrosive agencies from deterioration due to exposure at high temperatures, for replacing mechanically worn material, for increasing dimensions or weight, for altering shapes and repairing surface defects and for developing decorative effects. It is an extremely flexible instrument and deposits metal layers of all kinds upon practically any sort of surface. These sprayed metal coatings then may be turned, ground, filed, milled, shaped or polished, because in spraying they become an integral part of the surface upon which applied.

Spraying Clay With Metals:
Great difficulty was encountered in interesting clay products manufacturers in their novel process. They simply were not interested, Mr. Binder said, protesting that glazes had been in use for centuries for coating clay bodies, and that there was nothing wrong with them. Determined to give his method a chance, Mr. Binder determined to buy the bisque shapes himself. Even this was found difficult, for he was compelled to go to plants and by undecorated pieces, making many personal trips for this purpose.

These pieces were coated and the beautiful metallic effects obtained were shown to a few ceramists, who remained unconvinced until some of the pieces placed in various shops, began to sell. This demonstrated that instead of being a competitor of ceramics, the metal-spray process might be used easily as an outlet for clay wares. Mr. Binder described the manner in which some commercially unsuccessful art pottery was treated with sprayed metal and sold at figures greatly in excess of the original prices. These vases, initially priced at $3.00, had been reduced to 75 cents in a vain attempt to make them sell. The glaze was removed by sand-blasting, and a metallic surface applied, the total labor cost involved being $2.25. The rejuvenated vases sold for no lest than $18.00!

The method employed is almost as simple as spraying ordinary glazes, and the equipment is installed with as little trouble as with glaze-spraying equipment. The spraying process, in reality, is a modification of foundry practice, wherein the cupola is charged with a metal, which, as it melts, is drawn and poured into molds. Practically, the same thing is done with the instruments here described, but in a different manner. Instead of taking raw material in the form of ore or pig or scrap, metal is used in the form of wire.

Operation of Equipment
This feeds automatically through the sprayer, as it is held in the hand, and into a melting oxy-acetylene flame. Compressed air is employed to carry, or practically pour the molten metal in the form of minute particles onto the surface being coated. The same stream of air serves to cool the surface.

In operation, the equipment is connected to a supply of acetylene, oxygen, and compressed air. It consumes about 15 cu. Ft. of each of the gases per hour and 50 cu ft (at 50 lbs per sq. in.) of compressed air per min. Metal in the form of standard gauge wire is pulled from a reel by feed rolls in the gear case and passes continuously at a uniform rate of from 12 to 24 feet per min. to the nozzle of the short barrel. Her the wire enters a continuous reducing flame zone and is melted, atomized and blown in a very fine molten spray onto the surface.

The spray covers a circle of about 2 in. in diameter on a surface 5 in. from the nozzle. Generally the nozzle is held about 4 in. from the surface. In this short distance the wire is changed from the molten state, thence to the spray, and instantly back to a solid and practically cold coating. The temperature of the surface raises but slighting, and it is possible to apply coatings to the most delicate objects. As evidence of the perfect control of the operation, the thinnest paper, fabrics or wood receive the impacting particles of the molten metal without charring, and delicate laces may be used as stencil for reproducing a pattern.

The instrument is traversed across the surface with a regular motion, a single pass developing a coating of about 0.001-in. The operator?s vision guides him easily in distinguishing between the coated and uncoated portions and also between successive coats. Coatings of any desired thickness may be applied.

Many successful applications of this process to clay products were displayed, some of which are here reproduced. Among the most interesting were clay spandrels which had been coated with aluminum, of considerable interest in view of the growing use of aluminum as a decorative material in building construction. Mr. Binder pointed out that in this way the durability of clay can be combined with the modern metallic decorative effects, thus offering several advantages over the plan metal now in vogue.

Brick, terra cotta, tile, pottery and other types of clay bodies can be coated in the same way. By polishing or not polishing the surface so treated, a variety of metallic effects and contrasts can be obtained, as can be seen in the vase on accompanying page.

Industrial Applications
In addition to the wide range of applications of the apparatus as an artistic tool, it has been found valuable in the industrial field as a means of applying protective coatings to metal or other surfaces. By a new development it can be used to coat the inside of pipes as small as one inch in diameter with metal. Slip tanks may be given a metal coating, surface defects in mechanical equipment, shafts and bearings parts may be filled with metal which then can be surfaced off. High-tension insulators have been coated on the inside to cut down corona discharge. Glass condensers are sprayed inside with molten lead and outside with molten copper, using this equipment

Some of the metals which can be applied are zinc, aluminum, lead, tin, copper, bronze, cadmium brass, German silver, nickel silver, nichrome, monel, iron, stainless steel, gold, silver, phosphor bronze, aluminum bronze, eutectic alloys, bismuth, selenium, manganese and tantalum. It may be said that the only metal which it has been impossible to use is tungsten. Chromium may be sprayed as a dust by another tool, but this is an expensive process. Platinum has been sprayed successfully as well. The tool is also being used as a means of spraying fused quartz in building up large lenses.

Discuss Expansions of Coatings
Red Whitaker, General Ceramics Co., Keasbey, NJ asked the speaker what effect the difference in expansion between the metal itself and the coating would have on its durability. In reply it was explained that a series of freezing and thawing tests had shown no effect on the adherence of the coating, the coatings were for all practical purposes, being non-porous in nature. Furnace and grate bars coated with aluminum and then heat treated to produced a coating of aluminum oxide have proven 300 to 400 times as durable as untreated bars. Superheated tubes and boiler tubes are made almost non-deteriorating by the metal coating process.

When questioned as to the cost of coating, Mr. Binder said that the charges came between 10 and 25 cents per sq. ft. for the material, depending upon the metal. In addition, there is labor cost, which varies according to the extent of cleaning, requirements of the surface. Pottery, of course, may be decorated in the bisque without cleaning.

Questioned about the danger of cracking the clay body, it was stated that the heat is dissipated at once by the stream of compressed air which follows that of atomized metal. The compressed air is made to do several things in this way. To show how fast cooling takes place, it is interesting to note that the hand of the operator can be held in the spray without becoming unduly warm.

Mr. Homer F. Staley, Metal and Thermit Corp, New York, inquired whether or not it was possible to re-heat the metal (below its melting point) for decorating purposes. This was answered in the affirmative, the speaker stating that in this way it might be possible to combine the process with the ordinary processes in glazing and enameling.

Reference was made to the fact that mandrels for bottle-making machines, made of the best steel available, generally give only one-half to 4 hours of service. When coated with metal by the equipment described, these mandrels have given up to 7 weeks? service representing an unusual substantial saving.

In response to another question by Mr. Whitaker, Mr. Binder said that the coating may be built up to almost any thickness within reason. The metal so applied will have the same strength and general properties which it possesses in more usual forms.