Oxydizing to Prevent Rust.
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An Account of the Bonternpi Rust-proofing Process.
There is very little to tempt the manufacturer of a commercial-vehicle model to brass or siiverplate those exposed portions of the chassis which cannot conveniently be coated with paint. Such an addition to the finish and appearance of the machine costs money, and in service it involves care and extra labour—increasingly-unattainable assets as tiThe goes. Metal cannot be left irs its uncoated state at the recrey of the atmosphere. Rust not only typifies neglect, but it is also detrimental, and seriously so in some cases, to the strength of the component part which it has attacked. There bas, therefore, it is evident, been a distinct demand for sonic simple and cheap rust-proofing process, which will preclude all possibility of oxydization of surface, and yet will not have the disadvantages and discomforts arising from the free use of ordinary paint. Galvanizing, whether by the more expensive electric process or "the more ordinary and rougher " pickling," is an expedient that does not lend itself to the proofing of finished machined parts. Moreover, it is not permanently rust
proof. Rust can get beneath the deposit, which, after all, is little more than a special way of painting.
The search for a method which should render exposed finished parts immune against oxydization is not a new one, and processes have been patented in past years which have met with a considerable degree of success.
We have, during the past week, had our attention drawn to a system of proofing for which a great advance in method is claimed. We refer to the Bontempi process, the invention of an Italian chemist, of which the British and British-Colonial -patents are controlled by the British Bontempi Rust-Proofing Co., Ltd., which has the first installation of its furnace in place on capacious premises at Creek Street, Deptford, SR We were prompted to investigate the methods and processes adopted with some considerable degree of care after having satisfied ourselves that the samples of all kinds which were submitted to us appeared to have been treated most effectively. The finish secured is a very pleasing one, and according to the material, the time of treatment, and oilier factors in the routine, is of shades of slatish blue.
Mr. L. G. Davies, the engineer of the company, showed us, on the occasion of our visit, sampleawhich had been exposed for months to oxydizing conditions, and which appeared to be quite rust-proof. These samples included chains, small forgings and stampings. and malleable and cast-iron specimens of all
kinds. There is no doubt whatever that the whole of the articles, alter a_ simple preliminary preparation, were effectively " Bontempied." The only criticism which we were able to make was in respect of isolated pin-points of rust on one or two of the rougher examples out of a great number of items. These pinpoints Apparently were present owmgato the fact that slight pimples, shall we say, had been present on the articles before they were processed. These elevations had been, of course, duly oxydized, but in rough handling afterwards had become knocked off and had left their minute bases exposed. They cannot spread. Such rust spotswere, as we say, remarkably few and were only detected by very careful search. They would not matter in practice,. and moreover would be eaSy to avoid, if sodesired, by care in the preliminary cleaning and smoothing. In all but these one or two minute eases the proofing was remarkably effective and complete, and we are left in little doubt, in view of the low oosr at which this can be effected, that this process, ;which not only enables the articles so treated to resist atmospheric and water oxydization, but also makes them proof against acid attack, a very .valuable characteristic.
We were shown, amongst other special samples, articles with brazed-jointed portions, and these had apparently gone through the ovens and been treated effectively without in any way weakening the joint. In the proofing of modern high-grade, heat-treated steels, there is a reduction of the tensile strength of the material, but in respect of the lower grades of steel, and malleable and cast-iron, we are informed that such change is negligible. Those are points upon which, of course, manufacturers will assure themselves when they investigate the claims of this process with a view to adopting it for handles, brackets, and fittings of all kinds on commercial-vehicle chassis. The photographs which we reproduce will in all probability interest our renders. They are illustrative of the first installation at Creek Street, which is now kept fully occupied not only in dealing with current orders, but in proofing large numbers of samples which, we ourselves_ noted. had been submitted by prominent engineering firms of all kinds throughout the country. The result is impregnation. The plant appears at first sight to be more complicated than it really is. It consists essentially of a 'tumbler drum—which, by the way, is of particularly ingenious design and of slow revolution, a big oven, a superheated-steam-generating plant, and a furnace, gas-heated, for treating the several special chemicals which are delivered as gases into the oven after the articles placed therein have been properly cooked and treated with superheated steam.There is nothing 'more in it than that. The simplicity of the routine is attractive and of course accounts for the cheapness of the process. The articles to be proofed are scoured in the tumbler by blast-sprayed hard steel dust. They are treated with caustic soda if there be any suspicion of grease or other deleterious coating. They then pass through the oven in the manner already described, and after two hours therein are taken out. and, by a special ingenious means, allowed to cool very slowly. They are then dipped in whale oil, and a bath of sawdust renders them finally ready for delivery, after inspection. This method is, of course, merely a scientific way of oxydizing and fixing the oxydization in order to prevent rust-formation — to prevent oxydizing, in other words, Inquiries and samples should be addressed to the Creek Street depot at Deptford, to the British Bontempi Rust-Proofing Co., Ltd.