US2255979A - Method of applying protective coatings to sheets - Google Patents

Description

tive, where sharp bends, such as required to form outer side of the bends, which are made in the "the sheet is largely lost. This is true, as has been of the bend, inasmuch as the-injury in the coat- Patented Sept. 16,1941

' UNITED STATES PATE T" OFFICE lilETHOD or APPLYING rnorao'rrvn coa'r To SHEEI'S He L. Kohler, Kansas City, Mo Issignor to Andrew A. Kramer, Kansas City, Mo.

No Drawing. Application oetober a, 19:8,

Serial No. 234,051

4 Claims. 91-684) My invention relates to a method of applying My improved method of providing a protecprotective coatings to sheets, and more particutive coating can be utilized to cover the entire larl'y to a method of applying a protective coating area of a galvanized sheet, particularly advanto a galvanized steel sheet; This application is tageously for use in a tank that is filled with liqa continuation of part of my co-pending appli- 5 uid that may have an undesirable corrosive efcation Serial No. 144,029, filed 'May 21, 1937, feet on the usual zinc coating provided on such patented March'- 21, 1939, Patent No. 2,150,929. sheet. In such case the entire inner surface of It is an important purpose of my invention tothe tank sections, or sheets, fabricated to a shape overcome the difllculty previously existing in and size and punched with suitable holes for seusing galvanized metallic sheets having a heavy curing the ons er, may be treated 1 coating of galvanizing, which was that thecoatmake the same more resistant to corrosion, not ing of zinc on the sheets would tend to crack, only at the bends therein, if there are any in and peel or flake off at the bend when making a the section, but over the entire surface thereof sharp bend. As pointed out in the above menexposed tosuch corrosion. I tionod patent, th damage thus caused to the It is a particular object of my invention to progalvanizing coating, particularly where a heavy. vide means for curing a defect in the coating at coating of galvanizing is provided on the sheet, a bend in a galvanized sheet, by treating the will render the coating at least partially ineflfecsheet in accordance with my method only on the flanges, or seams, are made, and as a result the h t in f m n fl n 1 em thereon, as advantage of the heavy galvanizing coating on h n coating is not injured on the inner sidepointed out in said above mentioned patent, be wing is due to the lack of tensile strength of the cause, at such ruptures in a galvanized sheet, n Whi h us s the r pturin or damasin the sheet would be no better than an uncoated f he o ing on the outer side of the bend.

sheet in resisting oxidization, or other corrosion, The heavier the coating of the zinc provided at the point of rupture, although the remainder I on the sheet; the greater the diflie l y in pleof the sheet would be well coated. venting cra ng of the alvanizing or zinc coat- My invention has for its purpose the provision i due to making a Sh bend in the sheet, 1 of a simple, but relatively inexpensive, method performing other operations on the sheet, that of providing means for protecting a sheet that mi ht rupture r cra k th same. this b in due has been fabricated, in a manner so as to preto the fact that the tensile strength of the same v t any corrosion thereof at a bend, or b nd is very much less than that of either the steel or other damaged areas thereof, due to fabrica- 5 e ferr u ne 110!, which lies adjacent the tion steps, even though the original zinc coating steel of e Sheet n e i' z S Mvi may have been damaged, or ruptured, inbending, vention not only entirely overcomes the diificulty or other fabricating operations. resulting from the up g 0 e c 8 It is a further important purpose of my invent. h ben or similar plac but makes the tion to provide a protective coating, either at a 511861; more resistant to corrosion, e h bend or over the entire area of a galvanized methe coating as be d. ruptured. at tallic sheet, that will be more resistant to corhe bend, at the pl s where the sheet is treated rosion, due to certain causes, than the galvanized n accordance With m m h d, than it was D i r sheet was before such treatment, and even before fabrication. in p r icularly resistant' t any fabrication steps thereof that might have corrosion due e S p Compounds P e n damaged the coating, were performed thereon, in 11 d S ilar mater als. and which protective coating will resist every I a mp sh th s pur os by a alsam t s kind of corrosion equally as well, as does the m cu y with the protective coa i ev galvanized sheet at the portions thereof that it is desired to make the same more resistant to have had only the heavy galvanizing ooatin 'apcorrosion, whether it be only at a rupture in the plied thereto prior to its fabrication. As the a vanizing coatin of Sueh 8 Sheet Over the term 'is used herein, by fabrication is meant, entire surfaceofthe sheet. Mercury. and amalany bending, cutting or punching operation, or s f r ry re par c lar y resistant to an other operation, on a sheet, that may b percorrosion due to acids, such as sulphuric acid, and

formed on the sheet after the same has been h r acids, and are not afiected by hydrogen rolled and galvanized. sulphide, as is zinc. Considerable difliculty is encountered in applying metallic mercury to a galvanized sheet to produce the amalgam coating, because of its extreme mobility and its high surface tension, which causes it to form globules, or drops, that run off the sheet, being thus difficult to handle and easily lost. By amalgamating lead with the mercury that is to be applied to the sheet, it can be applied in a much more satisfactory manner, and it is one of the important purposes of my invention to provide a protective coating on a sheet that has zinc thereon, by spreading or applying an amalgam of mercury and lead, or an amalgam of mercury and lead and tin, both of which freely amalgamate with mercury, to the surface to be protected.

It is a further purpose of my invention to provide such an amalgam that can be readily applied in the desired quantity to produce the protective coating desired, without destroying the crystalline structure of the zinc coating on a galvanized sheet, by merely spreading or rubbing the same on the parts of the sheet that are to be treated. In order to do this, I provide an amal gam of lead and mercury, or of lead, tin and mercury, that has the consistency of a soft putty, or is of a creamy character. If this is rubbed on the metal at the place where it is to be protected, such as a rupture in the coating on the sheet, a certain amount of the amalgam adheres to the surface of the sheet, both at the zinc coated area and the area where the coating has been ruptured. Due to the putty-like, or creamy, character of the amalgam, thev excess can be readily removed with a cloth, or'in a similar manner, and saved for future use.

It is a particular purpose of my invention to provide an amalgam of the above; mentioned character, that can be applied to a'sheet that has been previously galvanized, in such a manner that the amalgam will act on thezinc coating, so as to amalgamate therewith, so that a zinc-lead-mercury amalgam, or a zinc-tin-leadmercury amalgam, is produced, which, while at first soft and capable of being rubbed off with the fingers, will, after twenty-four to forty-eight hours, he just as hard and have a similar appearance to the coating on the sheet before the amalgam was applied. p

It is a further purpose of my invention to provide a method of making a protective coating for metals, which protective coating contains mercury, comprising the step of dissolving in mercury finely divided lead. or finely divided lead and tin, both of which readily amalgamate with mercury, in such proportions as to form a soft putty-like amalgam paste. The lead and tin can be simultaneously amalgamated with the mercury, by utilizing a lead-tin solder for this purpose, the solder being, preferably, although not'necessarily, finely divided for amalgamation with the mercury. While this can usually be done at ordinary atmospheric temperatures found in the ordinary work shop, if any difficulty is encountered in dissolving the finely divided metal, such as lead, or lead and tin, or it is desired to increase the proportion of such metal, or metals, to be dissolved in the mercury, or to dissolve lead-tin solder that is not finely divided in the mercury, the mercury can be heated above the' atmospheric temperature for this purpose.

Other objects and advantages 'of my invention will appear as the description of the same proceeds. ,I desire to have it understood, however, that I do not intend to limit myself to the particular details described, except as defined in the claims.

My improved method is carried out on galvanized sheets that have .been fabricated to the desired size and shape, by bending, die-shaping,

cutting and punching operations, or any of these that may be necessary to produce the article, or sections of an article, of the desired shape from the sheet of metal. After the sheet has been fabricated, it is cleaned at the places at which the protective coating is to be provided thereon, usually by means of dilute hydro-chloric acid, or a solution of tin chloride, or antimony chloride, or lead chloride, or zinc chloride, or

cyanide of soda, to remove zinc oxide, oil and dirt from the galvanized sheet. This cleaning solution may be applied with a brush or swab of some character, and the excess may be removed with a cloth, or any other suitable means. When it is desired to apply the protective coating only at or adjacent a ruptured area on a galvanized sheet, or an area that may have been damaged to the extent of injuring the protective coating, or rupturing the ame, the galvanized sheets are cleaned only on the outer sides of all bends therein, or any other area at which the coating may have been ruptured, or damaged, and areas adjacent these bends, or other areas where the damage may have occurred. A zone at the place at which the rupture in the zinc coating may exist will thus be cleaned, and also a zone on each side thereof. I

A putty-like amalgam of mercury and lead, or of mercury and lead and tin, is made up prior to cleaning the sheets, or is made up in quantity to be used whenever necessary, said amalgam having such proportions of the metal, or metals, amalgamating with the mercury therein, to the quantity of mercury therein, as to produce a soft putty-likematerial of the consistency of thick paste, or cream. cur y and lead, or of mercury andlead and tin, that are usedrto produce this soft putty-like material, will vary-somewhat, dependent upon whether lead alone is used, or lead and tin is used, and also upon the atmospheric temperature existing, as the material must, of course, be of the soft creamy putty-like character at the temperature at which it is to be applied to the sheet. Thus in the winter time, when a lower temperature'is encountered, both in the atmosphere and in the material of the sheets themselves,-a larger proportion of the mercury to the lead, or lead and tin, must be used to produce the soft putty-like coating material. I have found that 65% of mercury and 35% of lead by weight will produce an amalgam of the desired consistency in the summer time, while in the winter time, when the temperatures are exceedingly low, it is frequently necessary to utilize an amalgam made for this purpose, that is made up of one part by weight of lead, to three or four parts by weight of mercury.

Substantially the same proportions are necessary where lead-tin solder is used, except in the case of alead-tin solder which contains 33 /3% lead and 66%% tin, which solder has a lower melting point than does the tin contained there- Such a solder can be combined with the mercury inthe proportions of at least 40% of the solder to 60% of the mercury in the summer time, or imder ordinary warm weather conditions,

The proportions of mer- I to be utilized, are dependent upon the melting points of the metals that are amalgamated with mercury and the temperature encountered. Thus, if the mercury is heated when the lead is added thereto, as much as 50% lead can be included in the putty-like amalgam, and as much as 50% of a lead-tin solder, containing 33%%- lead and 66%% tin can be included in an amalgam and produce a putty-like, soft creamy material for application to a sheet. If more than 50% of lead or such solder is amalgamated with the mercury while heated, the amalgam will not remain in a putty-like condition at the temperature at which it can be practically applied to the sheet.

In making up the putty-like, or creamy, pastelike amalgam, it is necessary that the lead that is to be dissolved in the mercury, or amalgamated therewith, is in a finely divided condition when it is to be amalgamated with the mercury. The lead can be in the form of any small particles, such as shavings, turnings, cuttings, or in the form of a powder or granules. The finely divided lead is stirred into the quantity of mercury that is to be utilized to make the amalgam in the proportions necessary, substantially within the limits above referred to. When a lead-tin-mercury amalgam is to be made, solder is ordinarily used for the lead and tin content of the amalgam, and if desired, the solder can also be utilized in such finely divided form as set forth above. If the solution, or amalgamation of the solder with soon as the amalgam contacts the zinc coating on the sheet, it begins to act thereon to amalgamate the zinc in the zinc coating with some of the mercury in the amalgam. Accordingly, in

brushing the amalgam back and forth over the ruptured area, some of the zinc of the galvanizing coating will be caused to be spread over the ruptured area, and any loose flakes, or particles, of zinc will be dissolved in the lead-mercury amalgam, or lead-tin-mercury amalgam, as the case may be, amalgamating with the mercury in such amalgam.

The action between the zinc and the lead-mercury amalgam, or the lead-tin-mercury amalgam, will continue until the amalgam has penetrated the entire zinc coating of the sheet down to, at least, the ferrous zinc alloy at the surface of the iron, or steel, of the sheet. As the zinc amalgamates with the mercury, the resulting amalgam will gradually become stiller and harder, as the greater the amount of other metal amalgamated with the mercury, the harder and stifier the amalgam will become. As a result, the penetration of the zinc by the lead-mercury amalgam will eventually produce a zinc-leadmercury amalgam protective coating on the sheet over the entire surface to which the lead-mercury amalgam has been applied, which has lost the soft character of the lead-mercury amalgam and will become as hard as the zinc coating'originally on the sheet. Similarly, the penetration of v the zinc by the lead-tin-mercury amalgam will the mercury, is to take place at a practical rate at room temperatures, such division into fine particles is necessary. If an unusually large amount of solder or lead is to be incorporated in the amalgam, it is necessary to heat the mercury to cause the material to be dissolved. Also if the solder is to be amalgamated with the mercury without finely dividing the same, or in other words, if relatively large pieces of the solder are to be dissolved, or amalgamated, with the mercury, the mercury must be heated to accomplish this in a practical manner. Inasmuch as the melting point of the solder is somewhat below that of the vaporization point of the mercury, heating up to the melting point of'the solder can be utilized to get quick solution of the solder in the mercury, even if the solder is in a large piece, or large pieces, without loss of any of the mercury by vaporization. Whenever either the lead content, or the lead-tin solder content, desired in the amalgam, is above that readily amaleventually produce a zinc-lead-tin-mercury amalgam protective coating over the entire surface to which this amalgam was applied, which has lost the soft character of the lead-tin-mercury amalgam, and will become as hard as the zinc coating originally on the sheet. It has been found that the use of an amalgam containing lead produces more rapid hardening of the amalgam coating on the sheet, than when a tin-mercury amalgam, for example, is used.

Thus, while the amalgam, when first placed on the sheet, will be soft enough that it can be rubbed off on the fingers to a certain extent, in the case of both the lead-mercury amalgam, and the lead-tin-mercury amalgam, after at least twenty-four hours, the coating at the area to gamating with the mercury at room temperature, the mercury may be heated for this purpose, keeping the temperature of the mercury well below that at which it would vaporize.

The soft putty-like amalgam of lead and mercury, or of lead, tin and mercury, produced as above described, is applied to the cleaned zone, or area, of the galvanized sheet, by a brushing or rubbing operation, the soft putty-like amalgam being brushed, or rubbed, onto the cleaned area of the sheet with a cloth, or in a similar manner. This rubbing or brushing operation spreads the lead-mercury amalgam, or the lead-tin mercury amalgam, as the case may be, overthe cleaned area of the sheet and causes athin layer thereof to adhere to the outer surface of the zinc coating on the sheet, and in case there is a rupture or damaged area in the sheet, from which the zinc has been entirely, or substantially entirely, re-

moved, the lead-mercury amalgam, or lead-tinmercury amalgamias' the case may be, will ad-' here to the sheet at ruptured area also. As

which the amalgam has been applied will be hard enough that none of the same will rub off and the sheet can be handled without any damage to the coating, just as readily as was the case with the zinc coating on the sheet originally. In fact, the lead-mercury amalgam, or lead-tin-mercury amalgam, when utilized as above described, will produce a protective coating on a sheet that will be practically as hard as was the zinc coating on the sheet originally, before such treatment, at

approximately twenty-four hours after application of the amalgam to the sheet. The sheet will, after the coating has become hard, have substantially the same appearance as it did before any amalgam was applied thereto, and none of thecoating can be rubbed off, even though it may be rubbed persistently for a considerable period of time. The coating will have the characteristic spangled appearance of the zinc coating originally on the sheet. This indicates that the application of the putty-like amalgam to the sheet that -hasbeen previously galvanized, while resulting in the dissolving of the zinc on the. sheet, in the mercury of the amalgam, does this in such a gradual manner that the liquefaction of the coating material on the sheet takes place at such a slow rate through the thickness of the zinc lead-mercury amalgam,

coating that the structure of the zinc coating on the sheet is not altered, although the composition changes from substantially pure zinc to a zinclead-mercury amalgam, or a zinc-lead-tin-mercury amalgam, as the amalgamating process proceeds through the coating. The sheet will accordingly have substantially the same appearance two or three days after the amalgam was applied thereto as it had before any application of amalgam thereto.

While my improved method is particularly applicable for use to prevent corrosion at ruptures in coatings on galvanized sheets at bends therein, or similar places, it is obvious that under certain conditions it would be desirable to apply the cleaning step and the coating step, not only to the area of a sheet on the outer side of a bend at and adjacent the bend, but also to the entire surface of the sheet, that is innermost when it is put in place as a wall portion of a container that is subjected to the corrosive action of sulphuric acid, or other sulphur compounds, which are ordinarily found in oil tanks, or similar receptacles. These sulphur compounds cause a corrosive action on the zinc coating of the sheet as ordinarily provided in oil and similar tanks. However, by utilizing my protective coating, including the lead-mercury amalgam, or lead-tinmercury amalgam, and applying it to the inner surface of an oil tank, or the sections of an oil tank, made up of sheets that have been bent, out and punched, this undesirable corrosive action is avoided entirely.

The tendency of the sulphur compounds, when acting on either of the amalgam coatings described, is to cause the mercury in the amalgam to form a protective film on the surface that is exposed to the action of the dilute sulphuric acid, or hydrogen sulphide, or other sulphur compounds, this causing some slight loss of some of the other metals from the coating, such as the zinc, lead and tin, but the mercury arresting this loss substantially immediately, due to the film forming action that it has.

There is substantially no loss of mercury in the carrying out of my method, because, if there is any excess of amalgam applied to the sheet, such excess can be removed with a cloth, such as the cloth by means of which the putty-like amalgam has been rubbed on the sheet, and the part thus removed saved for use on another sheet or other portion of the sheet. While it is immaterial whether the amalgam coating is of the same composition throughout, it has been found that if the soft putty-like amalgams, above referred to, are utilized, some of the mercury in the amalgams will amalgamate with the zinc immediately, forming either a zinc-lead-mercury amalgam, or a zinc-tin-lead-mercury amalgam, as the case may be, and some of the lead-mercury amalgam, or some of the lead-tin-mercury amalgam, as the case may be, will be present without any zinc in it at first, this being on the top surface of the coating. However, if the amalgams above referred to are left. in contact with the zinc coating for twenty-four hours, or more, and an excessive amount of the amalgam is not used, suflicient of the mercury will amalgamate with the zinc that all of the zinc will become amalgamated with the mercury, and the resulting .coating will be, in the case of the use of a a lead-zinc-mercury amalgam, and in the case of the use of a leadtin-mercury amalgam, the resulting coating will be a zinc-lead-tin-mercury amalgam, from the outer surface thereof to at least the ferrous zinc alloy at the surface of the metal of the sheet. Due to the fact that the zinc requires a much larger amount of mercury to be amalgamated with the same to produce a soft putty-like amalgam, than does lead or tin, this amalgamation of the mercury with the zinc, when completed,

causes the coating to have a hard character, similar to that of the zinc, instead of a soft puttylike character, such as the amalgams had before these were applied to the sheet.

When a putty-like amalgam containing 35% lead and 65% mercury by weight, is utilized for application to a galvanized sheet that has a coating thereon of zinc that amounts to one ounce per running square foot, or one-half ounce per square foot surface on each side of the sheet, the amalgam will contain approximately 74.4% zinc, 10.2% lead, and 15.4% mercury. If a puttylike amalgam containing 60% mercury and 40% by weight of a tin-lead solder that is made up of 33%% lead and 66%% tin by weight, is utilized for application to a galvanized sheet that has a zinc coating, such as above referred to, thereon, the amalgam resulting will contain approximately 70.85% zinc, 7.77% tin, 3.88% lead and 17.5% mercury. With a heavier coating of zinc, the percentage of zinc will, of course, be higher, and of course, the percentage of lead, or lead and tin, will be less in the case of an amalgam being used that contains a larger percentage of mercury. As in all cases the amount of zinc in the amalgam coating resulting on the sheet will be over 50%, the coating will retain the characteristics of a zinc coating to a considerable extent, but will be modified in its characteristics considerably by the mercury contained therein, and to a lesser extent by the lead, or tin and lead, contained therein.

What I claim is:

1. The method of increasing the resistance to corrosion of a galvanized metallic sheet having a damaged area in the zinc coating thereof produced by fabrication operations performed on said sheet after galvanization thereof, comprising the spreading of a soft, creamy putty-like amalgam containing lead and from 65% to mercury by weight over and adjacent the damaged area of said sheet, and removing any excess of said amalgam therefrom.

2. The method of increasing the resistance to corrosion of a galvanized metallic sheet having a damaged area in the zinc coating thereof produced by fabrication operations performed on said sheet after galvanization thereof, comprising the spreading of a soft, creamy, putty-like amalgam containing approximately one part lead to two parts tin and from 50% to 80% mercury by weight over and adjacent the damaged area of said sheet, and removing any excess of said amalgam therefrom.

3. The method of repairing a rupture in the zinc coating of a galvanized metallic sheet, comprising spreading thereby a soft, creamy, puttylike amalgam containing from 65% to 80% mercury by weight and lead over the surface of said sheet at and adjacent said rupture, rubbing the resulting amalgam over said rupture, removing all excess amalgam from said sheet and permitting the resulting amalgamation, over the entire area over which the same was spread, to proceed undisturbed throughout thezinc coating of the area of said sheet having 'ifid amalgam applied thereto to a stage resulting in a hard amalgam coating over said area.

4. The method of making a corrosion resisting coating having the appearance of a galvanizing coating on a galvanized metallic sheet, comprising making a soft, creamy, putty-like amalgam principally of mercury, lead and tin, containing from 50% to 80% mercury by weight, from16%% to 6%% lead by weight, and from 33 to 13 tin by weight, applying a thin coating of said amalgam to said sheet, removing excess amalgam from said sheet, and leaving said coating undisturbed until said amalgam penetrates and amalgamates with all the zinc on the area of said sheet having said amalgam applied thereto and said coating hardens after such complete amalgamation.

HENRY L. KOHLER.

CERTIFICATE OF CORRECTION. Patent No. 2,255,979. September 16, 19LL1.

HENRY L. KOHLER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1;, second column, line 614., claim 5, for the word "thereby" read 'thin ly--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of November, A. D. 19in. Y

Henry Van Arsdale,

(Seal) Acting Commis sioner of Patents.