US3615890A - Method of applying phosphate conversion coating by reverse roller technique - Google Patents

Method of applying phosphate conversion coating by reverse roller technique Download PDF

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Publication number
US3615890A
US3615890A US714217A US3615890DA US3615890A US 3615890 A US3615890 A US 3615890A US 714217 A US714217 A US 714217A US 3615890D A US3615890D A US 3615890DA US 3615890 A US3615890 A US 3615890A
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coating
solution
phosphate
chlorate
ferriferous
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US714217A
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Richard A Montella
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Suez WTS USA Inc
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Amchem Products Inc
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Assigned to AMCHEM PRODUCTS, INC. A CORP. OF DEL. reassignment AMCHEM PRODUCTS, INC. A CORP. OF DEL. MERGER (SEE DOCUMENT FOR DETAILS). Assignors: AMCHEM PRODUCTS, INC. (MERGED INTO), HHC, INC. (CHANGED TO)
Assigned to BETZ LABORATORIES, INC., SOMERTON RD., TREVOSE, PA. 19047, A CORP. OF PA. reassignment BETZ LABORATORIES, INC., SOMERTON RD., TREVOSE, PA. 19047, A CORP. OF PA. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: AMCHEM PRODUCTS, INC.
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
    • C23C22/08—Orthophosphates
    • C23C22/10—Orthophosphates containing oxidants
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process

Definitions

  • An acidic aqueous coating solution particularly suited for application to ferriferous surfaces by a reverse roller coating process that is a process wherein the coating solution is applied to a moving metal surface by means of a feed roller which is rotating in a direction opposite to that in which the metal surface is moving, the solution being effective to produce a phosphate conversion coating on the ferriferous surface and containing alkali metal phosphate or phosphoric acid and chlorate, the ingredients being present in relative amounts which are dependent on the pH of the solution which is within the range of about one to about 3 .5.
  • This invention relates to producing phosphate conversion coatings on metal surfaces. More particularly, this invention relates to phosphate-containing conversion coating solutions and to the application of such solutions to ferriferous metal surfaces by the reverse roller coating technique.
  • the source of the phosphate ion in the coating solutions to which this invention relates is an alkali metal phosphate, including ammonium phosphate, or phosphoric acid.
  • the reverse roller coating technique has a number of advantages over other techniques for applying conversion coating solutions to metal surfaces. For example, with respect to that method of applying coating solution by moving the metal surface past or over a roll or rollers which are rotating or moving in the same direction as the metal surface, the reverse roller coating technique has the advantages that the coatings can be applied to the surface with greater rapidity and without sacrificing coating quality; in many applications, an improvement in coating quality is obtained. These advantages are realized also when the reverse roller coating technique is compared with other application methods, such as spraying and immersion methods.
  • dwell time refers to the time period during which the coating forms on the surface and is measured from the time the solution is applied to the moving metal surface by the coating roller to the time excess or spent solution is removed from the surface, as by rinsing or squeegeeing.
  • the interrelated factors utilized in building into the coating process a dwell time period are the speed of the metal surface and the position of the equipment for removing excess of unused solution relative to the position of the coating roller.
  • the equipment for removing the excess solution must be positioned relatively far away from the coating roller, in which event plant space requirements are increased.
  • the speed of the metal surface would have to be slowed down to provide for the necessary dwell time period, in which event production would be reduced. It can be seen that a coating solution that requires a relatively long dwell time can tend to offset the high speed application advantages offered by the reverse roller coating process.
  • the dwell time for an industrial application process operating with satisfactory ferriferous surface speeds should be no longer than about 30 seconds and most preferably should be shorter.
  • this invention is directed to the provision of a phosphate-containing conversion coating solution having properties which reduce the severity of or avoid these problems and which allow the solution to be used in a reverse roller coating process which is operated at satisfactory industrial speeds with a dwell time of no longer than about 30 seconds.
  • a phosphatecontaining conversion coating solution which is said to have improved corrosion and cleaning properties, as well as coating properties.
  • the aqueous coating solution contains dissolved alkali and ammonium phosphates and undissolved ferric or aluminum phosphates, and can also contain an emulsifying agent.
  • the pH of the coating solution ranges from 5 to about 5 and it is emphasized that the pH should be kept within this range to obtain optimum performance.
  • the solution consists of an acid phosphate of an alkali metal and an oxidizing agent, including nitrites, sulfites, chlorates and bromates of the alkali metals.
  • the solution is said to produce coatings of increased thickness and improved paint adherence. It is disclosed also that the pH of the solution should not be substantially less than 4.2 if good paint adhesion properties are to be obtained and 6 is set as the upper pH limit.
  • U.S. Pat. No. 2,665,231 there is disclosed a phosphate coating solution containing an alkali metal phosphate and an alkali metal fluoride.
  • the coating solution is described as effective in minimizing the dissolution of iron, thereby reducing the tendency of sludge formation, and in eliminating corrosive action of the solution on equipment. It is further stated that the pH of the solutions should be between 3 and 5.8 because a lower pH gives too much pickling and a higher pH stops all pickling action.
  • the patents disclose a variety of coating solutions, which in addition to containing phosphate, also contain one or more additives for the purpose of obtaining an improved or specialized effect. Also, all of the coating solutions are acidic and the overall pH range is 3 to 6.5. (It is noted that in industrial practice, the solutions generally are operated at a pH between 4.2 and 5.8, the specific pl-i within this range being dependent on the chemical makeup of the solution utilized.) It is further noted that none of the patents is directed specially to a coating solution particularly suited to being applied to a ferriferous surface by the reverse roller coating technique.
  • the reverse roller coating technique can be utilized to apply the above described coating solutions to ferriferous surfaces to form thereon conversion coatings, none of them possesses properties which provide both for formation of the high quality coatings expected by industry and for the high speed production desired for economic reasons.
  • the overall result of this is that in the art of forming phosphate conversion coatings on ferriferous surfaces, it has not been heretofore possible to realize in an industrial scale process all of the advantages that are obtained by being able to apply the coating solution to the surface by the reverse roller technique.
  • the pH of the acidic coating solution of this invention can be as low as about 1 and is within the range of about 1 to about 3.5.
  • the amount of phosphate ion must be at least 5 g./l. and the amount of chlorate ion must be at least about 3 g./l.
  • the amounts of phosphate and chlorate must be at least about 20 g./l. and about 12.5 g./l. respectively. in general, but with some qualifications as will be explained more fully below, the minimum effective amounts of phosphate and chlorate that can be utilized increase as the pH of the solution increases.
  • the source of the phosphate ion in the solutions of this invention can be phosphoric acid or an alkali metal phosphate which when used herein and in the claims includes within its meaning ammonium phosphate, and also alkali metal and ammonium monohydrogen and dihydrogen phosphates.
  • the source of the chlorate ion can be any water soluble chlorate-containing compound which has a cation compatible with the other ingredients of the solution and has no deleterious effects on the coating solution or on the coating formed.
  • the chlorate is preferably added to the solution in the form of an alkali metal chlorate which when used herein and in the claims includes ammonium chlorate. Most preferably, the chlorate is added in the form of sodium, potassium or ammonium chlorate.
  • Examples 4-7 of the above table are set forth to show that when the pH of the solution is within the range of about 2.3 to about 2.8, the minimum amounts of phosphate and chlorate that can be utilized must be at least about 5 g./l. and about 3 g./l. respectively, provided that when one of the ingredients is present in an amount in the range of its minimum amount, the amount of the other ingredient must be greater than its minimum amount, and to the extent that when the chlorate is present in its minimum amount, that is about 3 g./l., the amount of the phosphate must be at least about 20 gJl. On the other hand, if the minimum amount of phosphate is utilized, that is about 5 g./l., then the amount of chlorate that is utilized must be at least about 12.5 g./l.
  • the minimum amount of phosphate utilized can be below about g./l., but in no event should it be below about 5 g./l., even if quite large amounts of chlorate are utilized.
  • the relative minimum amounts of each of the ingredients can be detennined quite quickly by following the rule that as the concentration of one of the ingredients increases, the concentration of the other ingredient can be decreased. For example, as the concentration of phosphate is increased from 5 g./1. on up to say about 20 g./ l., the minimum effective concentration of chlorate can be decreased from about 12.5 g./l.
  • the concentration of chlorate is increased from about 3 g./l. on up to about 12.5 g./l.
  • the minimum effective concentration of phosphate can be decreased from about 20 g./l. on down to about 5 g./l.
  • amounts of phosphate and chlorate utilized in the coating solution should not exceed about 20 g./l. and about 12.5 g./l. respectively. From the standpoint of forming a quality coating on the ferriferous surface, greater amounts are not necessarily detrimental and higher amounts can be utilized, such higher amounts being limited only by the solubility in the aqueous solution of the phosphate and chlorate compounds. However, when considering the economic aspects of the application process, it is important that the use of amounts of phosphate and chlorate in excess of about 20 g./l. and about 12.5 g./l. respectively be avoided. This is because the use of such higher amounts adds to the cost of the chemical constituents used in the coating solution, thereby adversely affecting the economics of the application process. Furthermore, in view of my finding that lower amounts of phosphate and chlorate are effective in providing a quality conversion coating, the use of higher amounts is not particularly justified.
  • the reverse roller coating technique can be utilized to apply phosphate-chlorate-containing coating solutions to ferriferous surfaces to form thereon a phosphate conversion coating, even if the pH of the solution is greater than about 3.5.
  • the pH of the coating solution be no higher than about 3.5. This is because to produce quality coatings at a pH of greater than about 3.5 the amounts of phosphate and chlorate that must be used in the coating solution are so high and the dwell time so long that the overall cost of the process tends to be high.
  • the coating process be operated with a solution having a pH in the lower ranges of about 1.0 to about 2.8. This is because lesser amounts of ingredients can be utilized in this range; moreover, it has been found that as the pH of the solution increases, the dwell time must be increased.
  • the application process is operated utilizing a coating solution having a pH ranging between about L8 and about 2.8. This is because relatively small amounts of the chemical constituents comprising the solution can be utilized to produce coatings that are excellent bases for final finishes. Moreover, such coatings can be produced within a relatively short dwell time.
  • the hydrogen ion content may be supplied by acids other than phosphoric.
  • acids other than phosphoric such as for example sulfuric, nitric or hydrochloric, may be added to the coating solution in amounts sufficient to impart to the solution the pH desired.
  • ferriferous as used herein includes within its meaning surfaces such as iron, steel and alloys of iron.
  • the ferriferous strip S is shown as being moved in the direction of the arrows by suitable means not shown. As areas of the strip come into contact with coating roller 2, which is being driven in the direction of the arrow 2A, coating solution is applied to the strip. The coating solution 3 is transferred from the container 4 to the surface of the coating roller 2 by roller 6, which is submerged in the coating solution, and the roller 10. Each of these rollers is moving in the direction of the arrows shown.
  • solution that remains on the strip must be removed therefrom. This is because if soluble salts are allowed to deposit and remain, the ultimate life of a paint finish applied to the resultant coating tends to be shortened. it will be appreciated that some of the solution will tend to drip from the strip into the collecting pan P. However, means should be provided to remove the remainder of the excess or spent solution. As shown in the drawing, squeegee rollers 29 and 30 are provided ro this purpose. Other appropriate means can be utilized to remove solution that remains on the strip, such as for example, a water rinse.
  • the coating solutions described herein have properties such that the dwell time for any particular coating solution need not be greater than about 30 seconds, which is a tolerable time period in that it does not appreciably add to the cost of the application process. it should be understood that longer dwell time periods than 30 seconds can be used, but without particular benefit.
  • the minimum dwell time this will vary from solution to solution. After the solution is applied, some period of time will elapse before the coating is formed. Therefore, some time period must be provided for before means are utilized to remove from the ferriferous surface the solution that has not taken part in forming the coating. In general, at least a 4-second dwell time period will be required. However, this may vary depending on the particular solution utilized and the minimum dwell time can be longer or shorter than 4 seconds. ln accordance with this invention it need not be longer than about 30 seconds.
  • Another aspect of this invention is the finding that improvements in the coating application process are obtained if the ferriferous surface is heated somewhat so that as the surface comes into contact with the coating roller surface, the temperature of the surface is above ambient, but is not so hot that it will cause the coating solution to dry before it reaches the means provided for removing excess coating solution.
  • An advantage obtained by applying the coating solution to a worm ferriferous surface is a reduction in the dwell time required to give optimum coatings. The problem encountered if the surface is so warm that the coating dries prior to being exposed to the means for removing excess or spent coating solution is that this solution will be more difficult to remove. it has been found that if the ferriferous surface has a temperature ranging between about 130 F. and about 140 F.
  • the heating of the ferriferous surface may be accomplished by any suitable means, for example by rinsing the surface with water hot enough to relatively quickly raise the temperature of the surface to somewhere between about 130 F. and about 140 F.
  • the amount of the solution that is applied to the strip is related to the speed of the surface of the coating roller and the opposing linear speed of the metal surface, other factors held constant.
  • This ratio of the roller surface speed to the opposing linear speed of the metal surface is generally expressed as a percentage. For example, if the roller surface speed is 120 ft./min. and the linear speed of the metal surface is 90 ftJmin. the ratio of the roller surface speed to the metal surface speed would be 120/90 or about 133 percent.
  • the coating solutions described herein are capable of forming acceptable coatings on ferriferous metal surfaces at roller surface/metal surface speed ratios of from as low as about 25 percent to as high as about 175 percent. This is an important characteristic of the coating solutions described herein because of the flexibility with which the rate of feed of the coating solution can be controlled. This characteristic is utilized to advantage when coat ing different types of ferriferous surfaces or strips, for example strips that are good" or easy" to coat, that is strips which readily accept a coating or strips which are bad or difficult to coat, that is strips which do not readily accept a coating. With respect to "good strips, roller surface/metal surface linear speed ratios as low as 25 percent can be utilized, whereas with bad" strips, the ratios utilized can be upwards of 100 percent.
  • cold water rinse 3. cold water rinse 4. water rinse at 130 F.-140 F.
  • stage (1) The alkaline cleaner used in stage (1) was applied by spray means.
  • Stages (2) and (3) utilized old water spray means while stage (4) applied a warm water rinse by spray means.
  • the water in this stage was kept just warm enough so that when coating solution was applied at stage (5), the heat did not cause the treated steel to dry prior to reaching the rinsing stage (6).
  • the water in rinse stage (4) was not so hot as to cause drying of the steel strip during the dwell time required for formation of the phosphate coating.
  • stage (7) there was utilized an acidulated rinse containing partially reduced hexavalent chromium at about a 0.07 percent concentration on a volume to volume basis.
  • the impact tests for determining adhesion were carried out by dropping a i-inch ball with a force of -inch pounds on the painted test panel, usually on the reverse side, and then checking for peeled and/or cracked paint.
  • the coating solution of this invention can contain ingredients other than the chlorate ion and the phosphate ion coating-producing ingredientsacids other than phosphoric being examples of such other ingredients.
  • other constituents can be added to the coating solutions for the purpose of obtaining specialized effects, surfactants and wetting agents being examples.

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
US714217A 1968-03-19 1968-03-19 Method of applying phosphate conversion coating by reverse roller technique Expired - Lifetime US3615890A (en)

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US71421768A 1968-03-19 1968-03-19

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US (1) US3615890A (xx)
BE (1) BE729966A (xx)
DE (1) DE1914052B2 (xx)
FR (1) FR2004260A1 (xx)
GB (1) GB1224115A (xx)
NL (2) NL6904207A (xx)
SE (1) SE346340C (xx)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5029439A (xx) * 1973-07-19 1975-03-25
US20030030282A1 (en) * 2001-08-08 2003-02-13 Denso Corporation Chemical treatment of helical splines in starter
US20040118483A1 (en) * 2002-12-24 2004-06-24 Michael Deemer Process and solution for providing a thin corrosion inhibiting coating on a metallic surface

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5891268A (en) * 1996-12-06 1999-04-06 Henkel Corporation High coating weight iron phosphating, compositions therefor, and use of the coating formed as a lubricant carrier

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5029439A (xx) * 1973-07-19 1975-03-25
US20030030282A1 (en) * 2001-08-08 2003-02-13 Denso Corporation Chemical treatment of helical splines in starter
US6819005B2 (en) * 2001-08-08 2004-11-16 Denso Corporation Chemical treatment of helical splines in starter
US20040118483A1 (en) * 2002-12-24 2004-06-24 Michael Deemer Process and solution for providing a thin corrosion inhibiting coating on a metallic surface
CN1754009B (zh) * 2002-12-24 2011-10-19 坎梅陶尔股份有限公司 在金属表面上提供薄腐蚀抑制涂层的方法

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Publication number Publication date
NL136910C (xx)
SE346340C (sv) 1979-12-20
FR2004260A1 (xx) 1969-11-21
NL6904207A (xx) 1969-09-23
GB1224115A (en) 1971-03-03
BE729966A (fr) 1969-09-01
DE1914052A1 (de) 1970-06-18
SE346340B (xx) 1972-07-03
DE1914052B2 (de) 1971-12-30

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Owner name: AMCHEM PRODUCTS, INC. A CORP. OF DEL.

Free format text: MERGER;ASSIGNORS:AMCHEM PRODUCTS, INC. (MERGED INTO);HHC, INC. (CHANGED TO);REEL/FRAME:004102/0461

Effective date: 19810320

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Owner name: BETZ LABORATORIES, INC., SOMERTON RD., TREVOSE, PA

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:AMCHEM PRODUCTS, INC.;REEL/FRAME:004722/0639

Effective date: 19870414