AND METHOD OF, POLISHING FERROUS COMPOSITIONS

Field ?,rιd Background of, Invention This invention relates to compositions and methods of using the compositions in preparing ferrous metal co ponents or subsequent surface electrop lating by preparing a solution containing an aci and sequestering agents, immersing the components and abrading media in the solution, and agitating the components and the abra- cl ing media whi le maintaining the components and the media immersed in the solution. Simi lar technology has been known heretofore from such d isc losures as Hays United States Fatent 2,890,944; a series of United States Fatents to Herman Ben Sπyder including 2,940,838; 2,981,610; 3,052,582; and 3,061,494; and Michaud et al United States Patent 4,491,500.

In accordance with the improvements of the present invention, the compositions are in dry granular form. In dry granu lar form, the composition has, by weight percent, up to about 40? of oxal ic acid crystal s; up to about 30? of a crystal l ine phosphorus sequestering agent; the ratio by weight of oxal ic aci crystal s to sequestering agent crystal s being in a range of from about 2:1 to about 0.4:1; a quantity of a l iquid amine ammonifying agent sufficient and effective for adjusting the pH of the solution formed on dissolving- the composi¬ tion in ater to about 3.5; a quantity of a non-foaming non- i on iG -surfactant sufficient and effective for accom-

pl ishing wetting of the composition; and a quantity of a granular absorbent sufficient to make up the remainder of the composition and effective to absorb said l iquid amine ammonifying agent and serve as a carrier therefor. " It has been known heretofore in the manufacture of ferrous metal components that electroplating of such componenls may serve the dual functions of protecting the ferrous material against rust or other deterioration and enhancing appearance. For such reasons, it is com- πionly done to plate hand tools such as wrenches and the l i e wi h bright electroplate f inishes. In preparing components for such finishing, it is Important that the surfaces to be lated have a certain degree of smoothness for appearance sake, and sometimes important h they be pol ished. hi le such pol ishing has been

» done in a number of different ways, chemical processes for metal removal have achieved some success and accep¬ tance, and have fol lowed general ly the teachings of the prior patents l isted above. In processes of the type described, there is a constant balancing of harshness against ro uctivity. In attempts to achieve high productivity of components and s ort cycle times for the use of equipment, some users have attem ted the use of strongly acidic sol u- tions. In attempts to achieve desirable surface f ini¬ shes, other users have attempted the use of less acidic solutions. In both instances, problems may be encoun¬ tered w ith exhaustion of solutions used and eff luents

created. Attempts at prolonging the useful ness of solu¬ tions have i nvol ved the use of sequesteri ng agents to avoid exhaustion of orking sol utions. i.I_J_ϋ-t _2≤iL££-U i-L.2Jl 2-L I πven.il≤.π. Hav i ng i n m i nd the efforts made i n the past and the prob lems encountered, it is an object of this inven¬ tion to ach ieve chemical ly smoothed surfaces for recei¬ ving bright electropl ated finishes in an optimal proces¬ s i ng ti me and w ith m i n i ma l undes i rab l e eff l uent. I n real izing this object of the invention, a process of the general type brief ly described hereinabove is improved by the use of _. an organ ic ac id sol ution wh ich ach ieves control led metal removal at a desirab l e rate. Produc¬ ion capab i l ities usi ng the sol ution contemp l ated by is invention are bette than these accompl ished using the harsher sol utions previous l y used, wh i l e the ef¬ f l uent rom the process more nearly approaches a chemi¬ cal ly neutral waste.

Y t another object of his invention is to provide co pos itions wh ich may be formu l ated and hand l ed as a dry granul ar material, then mixed w ith water to provide the necessary orking sol ution as needed. In real izing this object o the invention, the handl i ng and prepara¬ tion of the working chemical s used in the process brief- ly described hereinabove is simpl if ied for those users who ay prefer a dry granular material for that purpose. £_3i._l.LL.e.d D.es.£Elp.iiρl of, l.nyent i on Some of the objects of the i nvention hav i ng been

stated, other objects wi l l appear as the description proceeds. While the present invention w l l be described more ful ly hereinafter, it is to be understood at the outset of the description which fol lows that persons of ski l l In the appropriate arts may modify the invention here described whi le stil l achieving the favorable re¬ sults of this invention. According ly, the description which fol lows is to be understood as being a broad, teaching disclosure directed to persons of ski l l In the appropriate arts, and not as l imiting upon the present invention.

Stated general ly, the compositions contemplated by the present invention are dry granular compositions, hich are adapted to be mixed w ith water and used in a et process abrasive f inis ing apparatus for ferrous metals, such as a tumbl ing barrel or the l ike. The dry composition comprises, by weight percent, up to about 40? of oxal ic acid crystals; up to about 30? of a crys¬ tal l ine phosphorus sequestering agent; the ratio by weight of oxal ic acid crystals to sequestering agent crystals being In a range of from about 2:1 to about 0.4:1; a quantity of a l iquid amine ammonifying agent sufficient and effective for adjusting to about 3.5 the pH of the solution formed on dissolving the composition in water; a quantity of a non-foaming non-Ionic surfac¬ tant sufficient and effective for accompl ishing wetting of the composition; and a quantity of a granular absor¬ bent sufficient to make up the remainder of the composi-

tion and effective to absorb said l iquid a ine ammoni¬ fying agent and serve as a carrier therefor.

The phosphorus sequesteri ng agent may be any of the inorganic phosphates hich display the character is- tic of sequestering ferrous etal ions, and/or many of the organic phosphates hich display such characteris¬ tics. Those which have been found to perform better in the compositions of this invention are pyrophosphates, tr i poI yphosphates, and phosphonates. That which is most preferred is tetrosodi m pyrophosphate.

The buffering and/or ammonifying agent(s) may be any ammonia releasing or generating material which wi l l have the effect of moderating the pH of the solution. It has been determi ned that the combi ned effect of the acid constituent in removing metal and the sequestering agent in holding metal ions in solution and preventing their re-deposition onto the components in a p lati ng type process is pH dependent, and i l l not start and/or proceed properly at pH level s elow a out 3.5. Thus it is important, in the compositions and methods contemplated by this invention, to control that factor. A preferred material to accompl ish such control is mcncethanol amine. Monoethanolamine is a l iquid, and in order to acco pl ish its use in a dry granu lar material as contemplated by this invention it is necessary to incorporate a carrier for t e l iquid. That is done by use of an absorbent, and a preferred material is dia¬ to aceous earth, hich is essential ly chemical ly inert

for purposes of the present com osition and methods using the composition.

In order to assure that the compositions of this invention more easi ly enter solution ith water which mixed for use, it is desirable to incorporate a wetting agent in the form of a surfactant. A preferred surfac¬ tant Is a non-foaming, nonionic material, and it is further preferred that such material be of a low HLB type. The ratio of oxalic acid to sequestering agent is significant in balancing speed of metal removal to ac¬ compl ish surface f inishing against etching from exces¬ sively aggressive m tal removal inasmuch as both the materials used contribute to metal removal. Experimen- tation ith variations In the rai io cf acid to seques¬ terin agent ave s own tha , as a general matter, increasing the quantity of sequestering agent in rela¬ tion to acid increases the speed of metal removal and also increases the l ikel ihood that metal removal causes a distinctive "frosty" appearance which is deemed et¬ c ing and hich experience has sho n must be pol ished before satisfactory plating can be accompl ished. V/hi le the mechanism leading to such resu lts is perhaps not ful ly understood, it is bel ieved l ikely that the varying concentrations cause varying rates of effectiveness of metal removal in the microscopic level "peaks and val¬ leys" or roughnesses of the components. there etal removal is essential ly the same in both areas, a frosty

finish results. Where metal removal occurs more heavi ly at the peaks, a greater smoothness is achieved and the finished component is more acceptable. Depending in part upon the specific ferrous al loy being worked, r a- tios of acid to agent in the range of from about 2 parts to 1 part to about 0.3 part to 1 part have been found acceptab le and are contemp l ated by this invention. A preferred range is about 1.4 parts to 1 part.

In use, the compositions of this invention may be used in any known type of wet abrasive finishing equip¬ ent capab le of w ithstanding the corrosive effects of the dispersions which result. Examples of such equip¬ ment are l isted in the prior patents l isted above, and may include open and closed tumbl ing barrels, spinning machines, vibrating machines, and spind le machi nes. Such equipment may be capable of batch processing, con¬ tinuous or flow through processing, or both. Solutions used may be batched or recircul ated. The choice of such equipment is l ft to the ski l l of the person ski l led in the appl icab le arts and learning of this invention. However, as brought out ore ful ly herein¬ after, a preferred process uses apparatus arranged for rec i reu I at i on of the solution.

As briefly mentioned above, a ethod of preparing ferrous metal components for subsequent surface electro¬ plating in accordance with this invention Includes the kno n steps of preparing a solution containing an acid and a sequestering agent, immersing the components and

abrading media in the solution, and agitating the compo¬ nents and the abrading media whi le maintaining the com¬ ponents and the media immersed In the solution.

It is to be noted that an apparent factor in the successful operation of compositions as contemplated by this invention arises out of the differing solubi l ities of sodium and ammonium oxalafes and the ferric/ferrous sodium/ammonium oxalafes formed when the compositions are added to the treatment vessels in which ferrous components are being finished. The fatter materials are significantly more highly soluble in water, contributing to i e finishing action sought and accompl ished by this i nveπtion.

The improvement contemplated by this invention, as practiced using the dry granular composition, comprises t e steps of preparing a solution by mixing w ith ater from about 8 ounces to about 12 ounces per gal lon of water of the dry granular composition described above, monitoring the pH level of the sol ution during agita- tϊon of the components and abra ing media, and respon¬ ding to onitored pH levels by adding an alkal i and thereby adjusting the pH level of the solution to main¬ tain such pH ithin a range of from about 4.5 to a out 5.0 throughout agitation of the components and abrading media. Preferab ly the agitation continues unti l such time as a soft blackish fi lm has formed on the surface of the ferrous components. Experi entation has deter¬ mined that optimum productivity is achieved ith a re-

circulating type of process and w ith the solution recir¬ cu l ati ng at a f l ow rate i n the range of from about 0.25 to about 1.0 ga l l ons per hour per cub ic foot of vol ume in the vessel occupied by the dispersion, components and abrading med i a.

Certain experiments conducted in the develop ent of thi s invention are ref lected in the ol low ing exam¬ ples.

Fxarnp I e 1 Using a laboratory size closed barrel tu b ler and a sma l l l ot of sockets f or socket wrenches, a sol ution o ater and a dry granu l ar compos i ti on was prepared.

The composition contained equal parts by weight of oxa- l ic ac i d crysta l s and phosphate, and as ixed w i th water i n a ratio of c ounces to a ga l l on of ater;

Ord i nary ousehol d c l ean i ng a on i a as ad ed to the sol ut i on i n a quantity suf f ic i ent to a just the pH to about 4, The ferrous metal components were tumb led for

8 hours, re oved and ashed. It as observed that surf aces of the socket s were smoothed and that a gray f i l had deve l oped on t e surf aces. The socket s were deemed to h ve surfaces acceptab le for pl ating.

Examp I e 2

Us i ng the tumb l er of Examp l e 1 and a s i m i l ar quant ity of ferrous meta l components, a sol ution was prepared i n a si m i l ar way us i ng a ratio of oxa l ic ac i d t o phosphate of 0.30:1. Ord i nary househol d c l ean i ng a mon ia was used as an ammon i fy ing agent. The compo-

nents processed were found to have the frosty surface appearance deemed indicative of improper metal removal. While acceptable for plating, the plated components were less attractive visual ly than those of Example 1. Exa p I e 3

A dry granu lar composition as prepared using oxal ic acid crystals and tetrosodium pyrophosphate in a ratio of 2:1. N'onoethano I am i ne was blended with dϊato- maceous earth in a ratio of about 0.33:1 unti l the d'tato ceous earth had taken up the l iquid amine. The acid and phosphate were then blended w ith the amine carrier in a ratio of about 1.5:1 to form a dry granular com osition. The dry granular composition of acid, phosphate, a.iine and carrier was then mixed with water in a ratio of 12 oαnces to each gal lon of water and used in a commercial size vibrafor-y bowl finishing apparatus io finish a large quantity of components. The compo¬ nents were processed for 4 hours, and ere found to have an acceptable finish and a smutty black fi lm. Example 4

A dry granular composition simi lar to that of Ex am pie 3 was prepared, with the addition of about 1? by weight of a non-foaming nonionϊc surfactant. The compo¬ sition was mixed with water in a ratio of 10 ounces to each gal lon of ater. It as observed that mixing of the l iquid finishing composition was improved over the composition of Example 3. The f inishing mixture as used in an open tumbl r barrel, recirculating f low sys-

tern to process hand tools. It was observed that metal removal began after about f ifteen minutes and that a satisfactory surface f inish was ach ieved in about 6 hours ti e. Example 5

A dry granu l ar composition was prepared usi ng oxal ic acid crystals and tetrosodium pyrophosphate in a ratio of 1.4:1. Monoet no I a i ne was blended with d i a- tomaceous earth in a ratio of about 0.4:1 unti l the d iatomaceous earth had taken up the l iquid amine. The acid and phosphate were then blended ith the a ine carrier in a .ratio of about 1.5:1 to form a dry granular composition. The dry granu l ar composition of ac id, phosphate, amine and carrier was then mixed with water in a ratio of 10 ounces to each gal lon of water and used in a commercial size vibratory bow l finishing apparatus w i f ^' h recircu lating f low to f inish a large quantity of components. The components were processed for 5 hours, w ith a recircu l ating f low rate of 0.8 gal lons per hour per cub ic foot of machi ne capacity and were found to have an acceptable finish and a smutty lack fi lm. hi le the examples here included i l l reflect the parameters varied in experimentation done during devel¬ opment of the present invention, the forms of the pre- sent invention preferred at the writing of this descrip¬ tion are a dry granu l ar composition which has as its constituents, by weight: 35? Oxal ic acid crystals; 28? an absorbent for a l iquid ammonifying agent, preferably

d i atomaceous earth; 25? crystal l ine phosphorus, prefer¬ ably tetrosodium pyrophosphate; 11? ammonifying agent, preferably monoethano1 am i ne; and 1? non-foaming nonionic surfactant. In the specifications there have been set forth preferred embodiments of the invention and, although specific terms are used, the description thus given uses terminology in a generic and descriptive sense only and not for purposes of l imitation.