Metals in Dairy Equipment

copper Ascoloyt Iron Edges bare § Enduro Type "A" § § Nickel Edges tinned** Mang.aluminum alloy* Tin Copper Retin$ Monel Metal Zinc Tinned iron Nickel silver Edges barett Edges tinned$$ Manganese aluminum alloy (AI.plated)* * Furnished by th e Aluminum Company of America.The aluminum is the pure metal in a soft condition.The manganese aluminum alloy consists of 1.25 per cent manganese and the balance aluminum.t Furnished by the Allegheny Steel Company.Aseoloy is an ordinary chromium steel alloy, containing approximately 12 to 16 per cent Cr, 0.5 per cent Si, 0.5 per cent Mn., 0.025 per cent P, and 0.025 per cent S. Allegheny Metal is a special chromium steel alloy~ containing 17 to 20 per cent Cr, 7 to 10 per cent Ni, and less than 0.5 per cent Mn~ 0.5 per cent Si, 0.025 per cent P, and 0.025 per cent S.Furnished by the Sorensen Speciality Company.This is copper coated with a tin preparation which can be applied to renew the tinned surface without use of flux.The tin coating was very heavy.The remaining metals were furnished by J. G. Cherry Company.§ Represents copper strips the cut edges of which were not tinned.** Represents copper strips the cut edges of which were tinned.tt Represents iron strips the cut edges of which were not tinned.~ Represents iron strips the cut edges of which were tinned.§ § Endure Type "A" is an ordinary or straight chromium steel containing 16.5 per cent to 18.5 per cent Cr, 0.5 per cent to 1.25 per cent Si~ and less than 0.1 per cent C, 0.5 per cent Mn, 0.03 per cent S, 0.03 per cent P, and 0.25 per cent Ni.Since completing this work our attention was called to other Endure products, such as Endure 18-8, a chromium=nickel steel.The present experiment refers to Endure Type "A" only.The solutions used consisted of 4 organic acids, 2 mineral acids, sweet and sour milks and cream~, and sour cream neutralized, as shown in tables 1 and 3.In all cases half-pint Mason jars with glass covers were used.Each jar contained 130 cc. of the liquid under test.This made possible submersion of one-half of the length of the strips in each case.The metal strips were cleaned by washing in a very dilute solution of tri-sodium phosphate.They were then thoroughly rinsed in water, wiped dry, dried in a vacuum oven and carefully weighed.After immersing the strips in the respective liquids the jars containing liquid and strip were sealed and held at the temperatures indicated in table 3.At the end of the test period, the metal strips were removed and again washed, rinsed, dried, and weighed as before.'The strips were examined for visible corrosion and the liquids for color, precipitate, and flavor, and in some instances for metallic salts.In the case of complete submersion of the metal strips the procedure was identical with that described above, with the exception that the strips were only one-half the length of those used in partial immersion. METALS IN ACID SOLUTIONSThe acids used were 1 per cent solutions of acetic, butyric, lactic, hydrochloric, and sulphuric acids, and 0.2 per cent solutions of citric acid.Solutions of such weak organic acids as lactic, butyric, citric, and acetic, usually encountered in milk products, were included in these tests chiefly for the purpose of determining the character and extent of action of the acids themselves, and of thus revealing what acids, if any, are most harmful and to what extent the non-acid constituents and other substances present in the dairy product cause corrosion of the metals.The two mineral acids--sulphuric and hydrochloric--were included chiefly to determine the limit of resistance to corrosion of the several metals. Results obtained in acid solutions.The weight losses or gains per metal strip are assembled in table 1.They are expressed in milligrams.The area submerged in the acid solution totaledx The strips were washed and dried in the above manner, rather than by the use of alcohol and ether, to facilitate removal of curdy material.This procedure proved justifiable as the result of numerous preliminary tests which demonstrated absence of noticeable change in weight.