US1632833A - Metal pickling - Google Patents

Description

Luz. COMPOSITIONS,

l w H re atta Jiihe 21, 1927.

UNITED STATES JAMES H. GRANELL, OF ELKINS PARK, PENNSYLVANIA.

PATENT OFFICE.

METAL PIGKLINGI Il'o Drawing.

This invention relates, generally, to pickling metal, particularly iron and steel, 1I 1 a pickle bath, and it consists in the provision of a regulator for causing the acid of the pickling bath to selectively attack unclean portions of metallic surfaces to the exclusion or substantial exclusion of the clean portions of the metal surfaces.

The principal objects of the invention are to prevent the pickle from attacking clean metal, or more accurately, clean portions of the surface of the metal; to avoid the escape of poisonous vapors from the pickle vat to obviate over-pickling and pitting the work; to economize in the consumption of acid; to avoid rusting of the pickled work; to reduce the labor of making up pickling baths; to minimize the amount of metal lost in pickling; to cause the pickle to concentrate its energy on the scale removal only; to remove rust and scale from threaded, machined, and polished stock even if of high carbon steel without marring the finish or altering the dimensions; to provide for the use of a wider range of pickling temperatures; to increase the efficiency of the picklin operation and to prolong the life of the pickling bath; to produce clean work; to speed up the pickling operation; and to keep the atmosphere of the pickling department free from rust forming or promoting elements.

In the art of pickling the metal is treated with dilute acids to remove rust and scale,

after which the metal is washed with water and dipped into an alkaline bath to remove the last traces of free acid. The acid removes the rust and scale but unfortunately from the pickling standpoint it attacks the cleaned metal itself, producing an evolution of hydrogen gas which escapes into the air, carrying with it a fine spray of the pickling bath producing an atmosphere of great rusting properties and one which is highly injurious to health. The attack of the pickle on the metal itself not only wastes valuable metal but also uses up the strength of the 1 acid which should be directed to removing the rust and scale.

By the present invention these objectionable features of the pickling process are overcome to such an extent that from a commercial standpoint they can be considered eliminated. To accomplish this in accordance with my invention I add to the pickling bath a regulating agent oringredient which Application filed April 15, 1926. Serial No. 102,311.

especially effective in connection with sulphuric acid, which is the acid generally used for pickling iron and steel.

In order to produce the pickle regulator of my invention, I animal or. vegetable materials n bearing proteid, such .as. albumi -noids, and condense the distillate to secure a liquid containing or constituting a pickle regulator which in association' with a pickle bath profoundly alters the action thereof on the work, making the action selective with respect to the surface condition of the metal. The proteid bearing material may, among other things, be hair, gri stle, hides, skins, fiesh, casein, ossein, elatine, etc. As a practical example gelatine may be used. This is placed in a still in the regular way. The still is then slowly heated until nothing remains but charred coke, and products of the destructive distillation are collected in a reservoir or condenser in liquid form. A little animal or vegetable fat added to the gelatine before distillation assists in the operation by better distributing the heat throughout the mass and increasing the yield of control material.

The substance or material which I have termed distillate may be used in toto but I prefer to use. the water insoluble portion only, because of its superior control" action. This insoluble portion apparently consists of a series of basic materials so proportioned as to exert a powerful control efiecta To produce a pickling bath according to my invention, I may use the following formula:

Water 1000.00 gallons, sulphuric acid (66 B.) 50.00 gallons, water insoluble portion of distillate .125 gallon.

The ingredients may be mixed in the order given or thendistillateamaymbe mixed with a small portion of the acid (one part ofthedistillate andthree' parts of the acid) tiiaaadedaaer the bath has been made'up. Thedistillate may be varied to increase or diminish its control action, and it is'evident to those skilled in the art that the amount and kind of acid may be varied to produce a strong or weak bath. An equivalent amount gallon, hydrochloric acid (1.20 sp. gr.) 1

of nitre cake or similar acid bearing material can be used to replace the free acid if desired.

Ihg water insoluble distillate dissolyes-in the acid batlihi'ith turbidity use selectively Eliecks the"attack*of"the acidonclean'm'etal,

eliminating to a large extent the generation of hydrogen. What little hydrogen is produced is caught in a blanket of foam produced by the effect of the distillate and held in the foam long enough to deposit all condensed moisture before it escapes to the air, thereby removing all possibility of an obnoxious atmosphere such as would cause rust and injure the health. The pickling bath may be used at any desirable temperature from ordinary room temperatures up to boiling, as such temperatures have no decomposing effect on the distillate, but as the activity of the acid increases with the temperature of the bath, more distillate should be used as the temperature is increased. The amount of distillate given in the formula is suitable for pickling baths run at approximately 17 5- F. Generally stated, the amount of distillate required is that which will prevent the visible generation of hydrogen, known commercially as gassing. owever, I have found in certain cases where a large amount of distillate is required that an excessive and objectionable foam is produced which clings to the work and ma'rs its appearance, especially where the bath is highly heated.

This defect I have been able to correct by the discovery that the distillate consists of two component parts, one soluble in commercial hydrochloric acid and one that is not, and that the portion soluble in hydrochloric acid causes the pickle bath to act selectively and that the other portion produces the foam. I may therefore separate the extract into these component parts and use the acid soluble portion as my pickle regulator, which Iterm extract. To make the extract I m use the following formula:

Water insolu le portion of distillate 1 gallons.

The ingredients are thoroughly mixed which causes the generation of considerable heat, and then allowed to separate into two layers of liquid, the bottom layer being the extract, which I separate from the top layer by drawing off. Concentrated sulphuric acid cannot be used for this separation as it dissolves the entire distillate but equal volumes of sulphuric acid and water, forming a strong acid solution, may be used with satisfaction although I have found the yield is not quite equal to that of hydrochloric acid. My observations indicate that the presence of hydrochloric acid materially increases the control action of both distillate and extract.

Commercially I may use'the extract according to the following formula for pickling iron and steel:

Water 1000.00 gallons, sulphuric acid (66 B.) 50.00 gallons, extract .50 gallon.

This formula also produces a foam when acting on the metal but the foam is not as objectionable in character as produced by the distillate.

The described pickle control or regulator in the pickle bath restrains the action of the acid on free clean metal and therefore greatly diminishes the generation of hydrogen gas which action, in connection with the blanket of foam produced, entirely eliminates .the escape of all injurious and rust producing fumes. As my pickle regulator causes pra'ctically all attack of the acid to stop as soon as the scale or coating is removed, pitting and over-pickling are reduced as evidenced by the ability of my pickle bath to remove rust and scale from threaded, polished and machined parts without marring the finish or altering the dimensions. As the acid is prevented from attacking the metal no waste of metal or acid occurs as indicated by tests where a saving of 60% of the acid and 3% of the metal was noted. As acid is not wasted the same pickle bath will pickle a larger quantity of material, and, therefore, the bath does not have to be made up so often and hence there results a saving in the labor of making u pickling baths. Heretofore care had to e exercised not to have the pickle too hot or too strong in acid, or both, because there was danger of pitting or over-pickling the metal, but by my invention the temperature and the acid concentration of the bath may be eatly increased in order to diminish the t1me required for pickling, with less danger of pitting or overpickling.

It has been noted that steel tubes and other articles treated according to my pickling process drew with greater ease and resist rusting better than if pickled in the old way where only sulphuric acid is used, and it has also been noted that in drawing tubes pickled according to my invention, a peculiar odor is noted atthe dies. An investigation of these effects disclosed the fact that the acid of the bath causescertain o ti ons of the distillajftojbf'co'mg solubleffin the'fajijueous 5ath and that when the work, wet with tffiimsolutiaiiyis 'rieutralized'in the regular way by dipping with lime or other alkaline bath, the dissolved distillate is precipitated on the work in the water insoluble form and although in minute amount, acts to assist lubrication and rust prevention.

To those skilled in the art it will be evident that the composition of the distillate constituting the pickle regulator of the present invention, is complex, and that the philosophy of its action in causing a pickle bath to act selectively and to remove unclean or 252. COMPOSITIONS,

oxidized metal surfaces and to spare clean or bright metal surfaces is subject to various explanations, but from the foregoing description those skilled in the art will be able to practice the invention, which, for the reasons stated, is not limited to details of procedure, or to the precise ingredients mentioned, or to mere matters of form, or otherwise than as the prior art and the appended claims may require under and subject to the range of equivalents appropriate in chemical cases.

I claim:

1. A pickle regulator for selectively controlling the action of metal pickling baths comprising the portion of the distillate from animal bodies which is insoluble in water and is soluble in hydrochloric acid and in equal volumes of Water and sulphuric acid.

2. A pickle regulator for selectively controlling the action of metal pickling baths comprising the portion of the distillate from proteids which is insoluble in water and is soluble in hydrochloric acid and in equal volumes of water and sulphuric acid.

3. A pickle regulator for selectively controlling the action of metal pickling baths comprising the portion of the distillate from gelatine which is insoluble in Water and is soluble in hydrochloric acid and in equal volumes of water and sulphuric acid.

4. A pickling bath for metals one ingredient of which is the portion of the distillate of animal bodies which is insoluble in Water and soluble in hydrochloric acid.

5. Means for confining the etching action of a metal to oxidized portions of metal surfaces which comprise a pickle regulator being an acid soluble water insoluble distillate from animal bodies.

JAMES H. GRAVELL.