US 2298237 A
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Patented Oct. 6, 1942 2,298,237 LEAD BASE COATING ALLOY.
Albert A. Smith, Jr., N. J., assignors to and Paul A. Beck, Metuchen, American Smelting and Refining Company, New York, N. Y., a corporation of New Jersey No Drawing. Application March 7, 1941,
Serial No. 382,166
This invention relates to lead alloys suitable for coating sheet metal or other articles of a different metal base.
The principle of protecting ferrous metal bases from corrosion by the application of another metal or alloy thereto is well recognized and underlies the usual galvanizing and terning practises. However, the life of galvanized sheeting is materially shortened by sulphur compounds and the like commonly occurring in industrial atmospheres and of tin (commonly to in the usual terne-plate constitutes a serious economic threat to its extended use.
Various proposals have been made to employ lead alloys of much lower tin content than those ordinarily found in terne-plate but so far as is known none has proved entirely satisfactory. Thus, a lead-base alloy, containing only a few the relatively high percentage.
per cent of tin with an approximately equal no amount of copper and lesser amounts of antimony and zinc, has been suggested. While such alloy is considerably cheaper than the high tin alloy, it is disadvantageous from the standpoints of composition stability, fluidity temperature, etc.
The present invention provides an alloy composition admirably suited for application to ferrous-base sheets or other articles as a corrosionresistant coating; the resulting products being fully comparable to terne-plate for use in deep stamping operations, roofing, etc., but considerably cheaper than terne-plate from the standpoint of manufacturing cost.
Briefly, the invention contemplates the production of a lead-base alloy containing from l10% tin, 0.2-5% zinc and 0.2-3% antimony, the tin and zinc totalling not less than 3%, and the application of such composition to a ferrous base such as, e. g., sheet steel. Smooth, continuous coatings are readily applied using a typical composition of 5% tin, 2% zinc, 1% antimony,
balance lead and coating compositions containing only 2% tin have been successfully used. In general the tin content of the particular composition used should be about twice the zinc content to insure a homogeneous liquid just above the melting point (approximately 700 F.) of the alloy but the tinzzinc ratio can be much lower if a higher operating temperature (say 800 F.) is employed.
The following table ofiers a comparison, respecting hardness, between certain compositions falling within the limits hereinbefore specified,
on the one hand, and commercial lead and a 15% Sn alloy of lead on the other:
' Various procedures may, of course, be employed in applying the alloy coating to the sheets or other articles. Thus, the base may be immersed into a bath of the desired coating composition through a suitable flux and then withdrawn by suitable rolls, the thickness and character of the coating being controlled by the bath temperature, rate of travel of the base being coated, the position of the driving rolls with respect to the surface of the bath, and various other operating conditions and factors known to those skilled in the art.
Further, the application of the alloy may be varied to produce a variety of coatings. For example, bright, spangled coatings similar to those of zinc on steel have been produced by rapidly cooling steel sheets with an air stream just as they emerge from a typical bath containing one per cent zinc. For extremely smooth coatings, it has been found beneficial to employ alloys whose zinc content is in the upper part of the range. Obviously, various other modifications and changes in operation may be indulged in by those skilled in the art without departing from the'scope of the invention.
What is claimed is: V
1. An alloy consisting of 0.2-3% antimony, 0.2-5% zinc, 2-7% tin, and balance lead.
2. An alloy for coating a ferrous metal base consisting of the following approximate composition: tin 5%, zinc 2%, antiniony 1%, balance lead.
3. 'An article of manufacture comprising a ferrous base and a coating bonded thereto, said coating consisting of 0.2-3% antimony, 0.2-5% zinc, tin,- and balancelead, the zinc and tin totalling not less than 3%.
4. An article of manufacture comprising a ferrous base of sheet metal and a coating bonded thereto, said coating consisting of 24% tin,
0.2-5% zinc. 0.24% antimony. and balance lead.
ALBERT A. SMITH; .m, PAUL A. arzcx.