CA1261716A - Passivation of lead surfaces - Google Patents
Passivation of lead surfacesInfo
- Publication number
- CA1261716A CA1261716A CA000486844A CA486844A CA1261716A CA 1261716 A CA1261716 A CA 1261716A CA 000486844 A CA000486844 A CA 000486844A CA 486844 A CA486844 A CA 486844A CA 1261716 A CA1261716 A CA 1261716A
- Authority
- CA
- Canada
- Prior art keywords
- trivalent chromium
- lead
- aqueous solution
- ions
- present
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- 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
- C23C22/48—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 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
- C23C22/58—Treatment of other metallic material
-
- 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
-
- 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
- C23C2222/00—Aspects relating to chemical surface treatment of metallic material by reaction of the surface with a reactive medium
- C23C2222/10—Use of solutions containing trivalent chromium but free of hexavalent chromium
Landscapes
- 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)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for passivating lead and lead-containing surfaces comprising contacting the surfaces with an acidic aqueous solution containing trivalent chromium ions present in a passivation effective amount, under passivation effective conditions.
A method for passivating lead and lead-containing surfaces comprising contacting the surfaces with an acidic aqueous solution containing trivalent chromium ions present in a passivation effective amount, under passivation effective conditions.
Description
~2~7~Eii PATENT
Case D 7135 PASSIVATION OF LEAD SURFACES
BACKGROUND OF THE INVENTION
l. Field of the Invention This invention relates to the passivation of lead-containing surfaces using trivalent chromium acidic aqueous solutions.
Case D 7135 PASSIVATION OF LEAD SURFACES
BACKGROUND OF THE INVENTION
l. Field of the Invention This invention relates to the passivation of lead-containing surfaces using trivalent chromium acidic aqueous solutions.
2. Statement of the Related Art Numerous valuable specific properties, such as high resistance to corrosion, ready processibility, resistance to alternating thermal stress, favorable sound-insulating properties and high resistance -to che-micals, have resulted in a broad spectrum of applica-tions for lead and lead-containing alloys. Thus, lead-containing materials are being increasingly used in building construction, in the manufacture of chemi-cal equipment, in protection against radiation, in theautomotive industry and in other fields.
One of the reasons for this variety oE applica-tions is that, until now, lead and lead-containing sur-faces have not had to be separately protected a~ainst corrosion because they are self-passivating in air through the formation of stable coating5 of lead oxi-des, alkaline lead carbonates, lead sulfates or lead 6~7~6 sulfides of varying composition. In the past, lead and lead-containing surfaces have merely been subjected to alkaline cleaning which also resulted in a passivated surface affording adequate base for the application of other coating compositions, such as lacquers.
However, the relatively high toxicity of lead and certain lead compounds has necessitated an improvement in the protection against corrosion of lead and lead-containing surfaces. As a result, manufacturers of workpieces with surfaces of lead or le~d-containing alloys have had to meet stringent demands in regard to tne protection of their products against corrosion.
As the demands on corrosion prevention necessi-tated by new techniques for passivating lead and lead-containing surfaces have become more stringent, so toohave the demands imposed on manufacturers in regard to the adhesion of lacquers to lead and lead-containing surfaces. In the majority of cases, the above-mentioned salts formed during the self-passivation of lead surfaces in air do not permit sufficiently durable adhesion of subseguently applied coating materials.
Accordingly, there i9 a need to provide a method for the passivation of lead and lead-containing sur-faces which not only affords effective protection against corrosion, but also prepares those surfaces optimally for the subsequent application of lacquers and other coating materials.
DESCRIPTION OF THE INVENTION
The present invention affords a method for passi-vating lead- and lead-containing surfaces in which the surfaces in question, optionally after degreasing, are contacted with acidic aqueous solutions containing tri-valent chromium ions.
.:' -'`'''` '''" , : ' :
.,.. ,.,.. ,, ;, .. . , . ~
., ,:
~Z6~7~6 Thus, the present invention provides a method for passivating lead and lead-containing surfaces comprising contacting said surfaces with an acidic aqueous solution containing trivalent chromium ions preser.t in a passivation effective amount, under passivation effective conditions.
In another aspect there is provided a method for passivating lead and lead-containing surfaces comprising contacting said surfaaes ~ith an acidic aqueous solution having a pH of about 2 to about 6 at a temperature of about 20C to about 50C for at least about 1 minute, said solution consisting essentially of about 0.01 to about 10 g/~ of trivalent chromium ions.
- 2a -,~, .
. ~ ' ~' ':
.,.
. --: - ~ , ~' , ........
: '. ' :~ ' .. ' :
.: ~
~' : ~' ~'' ' ' - ~6~6 In the context o~ the invention, lead surfaces are understood to be surfaces of workpieces which consist entirely of lead or of another metal which has been coated with a surface of metallic lead produced electrolytically or otherwise. Lead-containing sur-faces are understood to be surfaces of workpieces which consist entirely of a binary or even higher alloy of metallic lead or of another metal which has been coated with a more or less thin surface of a binary or even higher lead-containing mixture.
Other than in the operating examples, or where otherwise indicated, all numbers expressing guantities of ingredients, reaction conditions, or defining ingre-dient parameters used herein are to be understood as modified in all instances by the term "about".
Aqueous solutions containing trivalent chromium ions in a quantity sufficient to effect passivation, more specifically 0~01 to 10 g/l preferably 0.02 to 5 g/l, are used for the method according to the inven-tion. Solutions containing trivalent chromium ions ina quantity of 0.4 to 3 g/l have proven to be par-ticularly effective in practice.
The trivalent chromium ions are introduced in the above-mentioned quantities into the solutions in the form of salts which dissolve readily in water in the temperature ran~e in which the method is cond~cted.
Salts of weak carboxylic acids are particularly suitable Eor this purpose. Examples include methanoate (formate), ethanoate (acetate), propanoate ~propionate), butanoate ~butyrate), ~,4-pentane dionate ~acetyl acetonate), and their mixtures. Trivalent chromium ethanoate is particularly preferred because the anion acts as a buffer in the solutions and, in addition, forms a complex with the trivalent chromium cation which shows sufficient stability to avoid 7~L6 environmental damage by the passivation solution.
To prepaxe the treatment solutions according to the invention, trivalent chromium ethanoate, or other salts may be used in analytical quality although this is not regarded as an advantage in view of the high costs. Commercial quality trivalent chromium etha-noate, or other salts, whose aqueous solutions generally have a p~ of from 3 to 5, is used for commer-cial application.
According to the invention, the aqueous solutions containing trivalent chromium ions have a pH of 2 to 6, preferably 3.2 to 4.2. This pH may be directly established simply by dissolving the commercial triva-lent chromium salt or dilution of its aqueous con-centrate in water, the pH should be outside the desired range of 2 to 6, ~or 3.2 to 4.2), it can be further ad~usted to the required level by addition of phosphoric acid or acetic acid.
According to the invention, phosphate ions may optionally be added to the passivating solutions. This is advantageously done by adding phosphoric acid to the solutions before their use in a sufficient quantity to result in 0.001 to 10 g/l preferably 0.01 to 5 g/l of phosphate ions.
The method according to the invention is conducted at a temperature in the range 20 to 50C, preferably 25 to 40C. Treatment times of as short as 1 minute are sufficient for achieving excellent passivation of the lead and lead-containing surfaces, even at the above temperatures.
In practice, the method according to the invention preferably is carried out by treating surfaces which have first been spray cleaned with any known alkaline aqueous cleaning solution for 60 to 180 seconds at 55 to 65Co Examples of suitable alkaline aqueous .
L2~7~i cleaners are: an aqueous solution containinF 1~ by wei~ht of a concentrat~, consistin~ of 3~Q0 so~lium hydroxi~e, 509 sodium triyhosphate, 20~ nonionic surfactant or 300 sodium hydroxide, 30~0 sodium orthophophate, 20% sodium carbonate, 20~ nonionic surfactant.
For passivation, the leaa or lead-containing sur-faces may be treated by spray-coating, dip-coating or by other known coating techniques, such as spray-dip coating or flood coating. The treatment time is generally l to 3, preferably l minute. The lead or lead-containing surfaces thus passivated are rinsed with water, further rinsed with partially ~or pre-ferably fully) deionized water and then dried with compressed air. Thereafter, it can be seen that a uni-form passivation layer has formed on the surfaces.
The lead or lead-containing surfaces passivated by the inventive method are eminently suitable for sub-sequent coating with paints, lacquers, and the like.
In particular, the lead surfaces thus passivated form an ideal substrate for polyurethane lacquers, although they are also suitable for other after-treatment processes.
The invention is illustrated by the following Examples.
EX~MPLE l .
A treatment solution containing 15 g of commercial trivalent chromium ethanoate in l liter of water (corresponding to 3 g~l o trivalent chromium ions) was prepared. The pH of this solution was approximately
One of the reasons for this variety oE applica-tions is that, until now, lead and lead-containing sur-faces have not had to be separately protected a~ainst corrosion because they are self-passivating in air through the formation of stable coating5 of lead oxi-des, alkaline lead carbonates, lead sulfates or lead 6~7~6 sulfides of varying composition. In the past, lead and lead-containing surfaces have merely been subjected to alkaline cleaning which also resulted in a passivated surface affording adequate base for the application of other coating compositions, such as lacquers.
However, the relatively high toxicity of lead and certain lead compounds has necessitated an improvement in the protection against corrosion of lead and lead-containing surfaces. As a result, manufacturers of workpieces with surfaces of lead or le~d-containing alloys have had to meet stringent demands in regard to tne protection of their products against corrosion.
As the demands on corrosion prevention necessi-tated by new techniques for passivating lead and lead-containing surfaces have become more stringent, so toohave the demands imposed on manufacturers in regard to the adhesion of lacquers to lead and lead-containing surfaces. In the majority of cases, the above-mentioned salts formed during the self-passivation of lead surfaces in air do not permit sufficiently durable adhesion of subseguently applied coating materials.
Accordingly, there i9 a need to provide a method for the passivation of lead and lead-containing sur-faces which not only affords effective protection against corrosion, but also prepares those surfaces optimally for the subsequent application of lacquers and other coating materials.
DESCRIPTION OF THE INVENTION
The present invention affords a method for passi-vating lead- and lead-containing surfaces in which the surfaces in question, optionally after degreasing, are contacted with acidic aqueous solutions containing tri-valent chromium ions.
.:' -'`'''` '''" , : ' :
.,.. ,.,.. ,, ;, .. . , . ~
., ,:
~Z6~7~6 Thus, the present invention provides a method for passivating lead and lead-containing surfaces comprising contacting said surfaces with an acidic aqueous solution containing trivalent chromium ions preser.t in a passivation effective amount, under passivation effective conditions.
In another aspect there is provided a method for passivating lead and lead-containing surfaces comprising contacting said surfaaes ~ith an acidic aqueous solution having a pH of about 2 to about 6 at a temperature of about 20C to about 50C for at least about 1 minute, said solution consisting essentially of about 0.01 to about 10 g/~ of trivalent chromium ions.
- 2a -,~, .
. ~ ' ~' ':
.,.
. --: - ~ , ~' , ........
: '. ' :~ ' .. ' :
.: ~
~' : ~' ~'' ' ' - ~6~6 In the context o~ the invention, lead surfaces are understood to be surfaces of workpieces which consist entirely of lead or of another metal which has been coated with a surface of metallic lead produced electrolytically or otherwise. Lead-containing sur-faces are understood to be surfaces of workpieces which consist entirely of a binary or even higher alloy of metallic lead or of another metal which has been coated with a more or less thin surface of a binary or even higher lead-containing mixture.
Other than in the operating examples, or where otherwise indicated, all numbers expressing guantities of ingredients, reaction conditions, or defining ingre-dient parameters used herein are to be understood as modified in all instances by the term "about".
Aqueous solutions containing trivalent chromium ions in a quantity sufficient to effect passivation, more specifically 0~01 to 10 g/l preferably 0.02 to 5 g/l, are used for the method according to the inven-tion. Solutions containing trivalent chromium ions ina quantity of 0.4 to 3 g/l have proven to be par-ticularly effective in practice.
The trivalent chromium ions are introduced in the above-mentioned quantities into the solutions in the form of salts which dissolve readily in water in the temperature ran~e in which the method is cond~cted.
Salts of weak carboxylic acids are particularly suitable Eor this purpose. Examples include methanoate (formate), ethanoate (acetate), propanoate ~propionate), butanoate ~butyrate), ~,4-pentane dionate ~acetyl acetonate), and their mixtures. Trivalent chromium ethanoate is particularly preferred because the anion acts as a buffer in the solutions and, in addition, forms a complex with the trivalent chromium cation which shows sufficient stability to avoid 7~L6 environmental damage by the passivation solution.
To prepaxe the treatment solutions according to the invention, trivalent chromium ethanoate, or other salts may be used in analytical quality although this is not regarded as an advantage in view of the high costs. Commercial quality trivalent chromium etha-noate, or other salts, whose aqueous solutions generally have a p~ of from 3 to 5, is used for commer-cial application.
According to the invention, the aqueous solutions containing trivalent chromium ions have a pH of 2 to 6, preferably 3.2 to 4.2. This pH may be directly established simply by dissolving the commercial triva-lent chromium salt or dilution of its aqueous con-centrate in water, the pH should be outside the desired range of 2 to 6, ~or 3.2 to 4.2), it can be further ad~usted to the required level by addition of phosphoric acid or acetic acid.
According to the invention, phosphate ions may optionally be added to the passivating solutions. This is advantageously done by adding phosphoric acid to the solutions before their use in a sufficient quantity to result in 0.001 to 10 g/l preferably 0.01 to 5 g/l of phosphate ions.
The method according to the invention is conducted at a temperature in the range 20 to 50C, preferably 25 to 40C. Treatment times of as short as 1 minute are sufficient for achieving excellent passivation of the lead and lead-containing surfaces, even at the above temperatures.
In practice, the method according to the invention preferably is carried out by treating surfaces which have first been spray cleaned with any known alkaline aqueous cleaning solution for 60 to 180 seconds at 55 to 65Co Examples of suitable alkaline aqueous .
L2~7~i cleaners are: an aqueous solution containinF 1~ by wei~ht of a concentrat~, consistin~ of 3~Q0 so~lium hydroxi~e, 509 sodium triyhosphate, 20~ nonionic surfactant or 300 sodium hydroxide, 30~0 sodium orthophophate, 20% sodium carbonate, 20~ nonionic surfactant.
For passivation, the leaa or lead-containing sur-faces may be treated by spray-coating, dip-coating or by other known coating techniques, such as spray-dip coating or flood coating. The treatment time is generally l to 3, preferably l minute. The lead or lead-containing surfaces thus passivated are rinsed with water, further rinsed with partially ~or pre-ferably fully) deionized water and then dried with compressed air. Thereafter, it can be seen that a uni-form passivation layer has formed on the surfaces.
The lead or lead-containing surfaces passivated by the inventive method are eminently suitable for sub-sequent coating with paints, lacquers, and the like.
In particular, the lead surfaces thus passivated form an ideal substrate for polyurethane lacquers, although they are also suitable for other after-treatment processes.
The invention is illustrated by the following Examples.
EX~MPLE l .
A treatment solution containing 15 g of commercial trivalent chromium ethanoate in l liter of water (corresponding to 3 g~l o trivalent chromium ions) was prepared. The pH of this solution was approximately
3.5.
Lead-coated steel sheets, which had been cleaned beforehand by spraying for 60 secs. at 50C with an alkaline cleaning solution, were sprayed with the above-mentioned treatment solution for 60 secs. at 30C~ The sheets were then rinsed with water and fully deionized water, dried by blowing with compressed air, ana coated with a Winkelmann polyurethane lacquer.
The sheets were then given a single cut in accord-ance with German Indusl-rial ~orm (DIN) 53,167 and .
" .:
~2~7~6 salt-spray-tested for 240 h. in accordance with DIN
50,021. Evaluation in accordance with DIN 53,167 revealed a creepage value oE <3 mm.
Evaluation of the de~ree of blistering in accord-ance with DIN 53,209 produced a value oE mO/gO.
A 1 liter aqueous solution containing 2 g/l of commercial trivalent chromium ethanoate (corresponding to 0.4 g/l of trivalent chromium ions) and 0.1 g/l of phosphoric acid (corresponding to 0.1 g/l of phosphate ions) was prepared. The solution had a pH oE 3.9.
Lead-coated steel sheets, which had been cleaned beforehand by spraying with an alkaline cleaning solu-tion for 60 secs. at 55C, were sprayed with the above-mentioned solution or 60 secs. at 40C. The sheets were then rinsed with water and fully deionized water, dried by blowing with compressed air, and coated with Winkelmann polyurethane lacquer.
The sheets were then given a single cut in accord-ance with DIN 53,167 and salt-spray-tested for 240 h.
in accordance with DIN 50,021. Evaluation in accord-ance with DIN 53,167 revealed a creepage value o <3 mm.
Evaluation of the degree of blistering in accord-ance with DIN 53,20q produced a value of mO/gO.
EXAMP~E 3 A solution containing 4 9/1 of trivalent chromium ethanoate (corresponding to 0.8 g/l of trivalent chrom-ium ions) and 0.3 g/l of phosphoric acid (corresponding to Or 3 g/l~l of phosphate ions) was pre-pared. The solution had a pH of 3.5.
Lead-coated industrial fuel tanks, which had been cleaned beforehand by immersion for 3 mins. at 65C in an alkaline cleaning solution, were immersed in the above-mentioned solution for 2 mins. at 22C. The . ., ::.- ~.. . .
l7~6 tanks were then rinsed with water and fully deionized water, dried by blowing with compressed air, and coated with a Winkelmann polyurethane lacquer.
The tanks were then given a single cut in accord-ance with DIN 53,167 and salt-spray-tested for 240 h.
in accordance with DIN 50,021. Evaluation in accordance with DIN 53,167 revealed a creepage value of <3 mm.
Evaluation of the degree of blistering in accord-anc~e with DIN 53,209 produced a value of mO/gO.
C ~ ~X~MPLE
Lead-coated steel sheets were cleaned by spraying wlth an alkaline cleaning solution for 60 secs. at 55C. The sheets were then rinsed with water and fully deionized water, dried by blowing with compressed air, and coated with a Winkelmann polyurethane lacquer.
The lead-coated steel sheets were then given a single cut in accordance with DIN 53,167 and salt-spray-tested for 240 h. in accordance with DIN 50,021.
Evaluation in accordance wi-th DIN 53,167 revealed a creepage value of >20 mm.
Evaluation of the degree oE blistering in accord-ance with DIN 53,209 produced a value of m5/g5.
The Comparison Example shows that the inventive method produces a distinct improvement in protection against corrosion, as measured by creepage value and degree of blistering.
,
Lead-coated steel sheets, which had been cleaned beforehand by spraying for 60 secs. at 50C with an alkaline cleaning solution, were sprayed with the above-mentioned treatment solution for 60 secs. at 30C~ The sheets were then rinsed with water and fully deionized water, dried by blowing with compressed air, ana coated with a Winkelmann polyurethane lacquer.
The sheets were then given a single cut in accord-ance with German Indusl-rial ~orm (DIN) 53,167 and .
" .:
~2~7~6 salt-spray-tested for 240 h. in accordance with DIN
50,021. Evaluation in accordance with DIN 53,167 revealed a creepage value oE <3 mm.
Evaluation of the de~ree of blistering in accord-ance with DIN 53,209 produced a value oE mO/gO.
A 1 liter aqueous solution containing 2 g/l of commercial trivalent chromium ethanoate (corresponding to 0.4 g/l of trivalent chromium ions) and 0.1 g/l of phosphoric acid (corresponding to 0.1 g/l of phosphate ions) was prepared. The solution had a pH oE 3.9.
Lead-coated steel sheets, which had been cleaned beforehand by spraying with an alkaline cleaning solu-tion for 60 secs. at 55C, were sprayed with the above-mentioned solution or 60 secs. at 40C. The sheets were then rinsed with water and fully deionized water, dried by blowing with compressed air, and coated with Winkelmann polyurethane lacquer.
The sheets were then given a single cut in accord-ance with DIN 53,167 and salt-spray-tested for 240 h.
in accordance with DIN 50,021. Evaluation in accord-ance with DIN 53,167 revealed a creepage value o <3 mm.
Evaluation of the degree of blistering in accord-ance with DIN 53,20q produced a value of mO/gO.
EXAMP~E 3 A solution containing 4 9/1 of trivalent chromium ethanoate (corresponding to 0.8 g/l of trivalent chrom-ium ions) and 0.3 g/l of phosphoric acid (corresponding to Or 3 g/l~l of phosphate ions) was pre-pared. The solution had a pH of 3.5.
Lead-coated industrial fuel tanks, which had been cleaned beforehand by immersion for 3 mins. at 65C in an alkaline cleaning solution, were immersed in the above-mentioned solution for 2 mins. at 22C. The . ., ::.- ~.. . .
l7~6 tanks were then rinsed with water and fully deionized water, dried by blowing with compressed air, and coated with a Winkelmann polyurethane lacquer.
The tanks were then given a single cut in accord-ance with DIN 53,167 and salt-spray-tested for 240 h.
in accordance with DIN 50,021. Evaluation in accordance with DIN 53,167 revealed a creepage value of <3 mm.
Evaluation of the degree of blistering in accord-anc~e with DIN 53,209 produced a value of mO/gO.
C ~ ~X~MPLE
Lead-coated steel sheets were cleaned by spraying wlth an alkaline cleaning solution for 60 secs. at 55C. The sheets were then rinsed with water and fully deionized water, dried by blowing with compressed air, and coated with a Winkelmann polyurethane lacquer.
The lead-coated steel sheets were then given a single cut in accordance with DIN 53,167 and salt-spray-tested for 240 h. in accordance with DIN 50,021.
Evaluation in accordance wi-th DIN 53,167 revealed a creepage value of >20 mm.
Evaluation of the degree oE blistering in accord-ance with DIN 53,209 produced a value of m5/g5.
The Comparison Example shows that the inventive method produces a distinct improvement in protection against corrosion, as measured by creepage value and degree of blistering.
,
Claims (21)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for passivating lead and lead-containing surfaces comprising contacting said surfaces with an acidic aqueous solution having a pH of about 2 to about 6 at a temperature of about 20°C to about 50°C for at least about 1 minute, said solution consisting essentially of about 0.01 to about 10 g/l of trivalent chromium ions.
2. The method of claim 1 wherein said trivalent chromium ions are present in the form of at least one organo-trivalent chromium salt.
3. The method of claim 1 wherein said trivalent chromium ions are present in the form of at least one salt of a weak carboxylic acid.
4. The method of claim 1 wherein said trivalent chromium ions are present in the form of at least one salt which is the methanoate, ethanoate, propanoate, butanoate, or 2,4-pentane dionate of trivalent chromium.
5. The method of claim 1 wherein said trivalent chromium ions are present in the form of trivalent chromium ethanoate.
6. The method of claim 1 wherein the pH of said aqueous solution is about 3.2 to 4.2.
7. The method of claim 1 wherein the pH is further adjusted to 2 to 6 by the addition of phosphoric acid or acetic acid or both.
8. The method of claim 1 wherein the pH is further adjusted to about 3.2 to 4.2 by the addition of phosphoric acid or acetic acid or both.
9. The method of claim 1 wherein phosphoric acid is added to said aqueous solution in an amount sufficient to result in about 0.001 to 10 g/l of phosphate ions.
10. The method of claim 1 wherein phosphoric acid is added to said aqueous solution in an amount sufficient to result in about 0.001 to 5 g/l of phosphate ions.
11. The method of claim 1 wherein said trivalent chromium ions are present in said solution in about 0.02 to 5 g/l.
12. The method of claim 1 wherein said trivalent chromium ions are present in said solution in about 0.4 to 3 g/l.
13. The method of claim 1 wherein said contacting is conducted at a temperature of about 25 to 40°C.
14. The method of claim 1 wherein said contacting is by means of spraying, dipping, flooding, or any combinations thereof.
15. The method of claim 4 wherein the pH of said aqueous solution is about 2 to 6, and the trivalent chromium ions are present in said aqueous solution in about 0.02 to 5 g/l.
16. The method of claim 4 wherein phosphoric acid is added to said aqueous solution in an amount sufficient to result in about 0.001 to 10 g/l of phosphate ions.
17. The method of claim 5 wherein the pH of said aqueous solution is about 3.2 to 4.2, and the trivalent chromium ions are present in said aqueous solution in about 0.4 to 3 g/l.
18. The method of claim 17 wherein phosphoric acid is added to said aqueous solution in an amount sufficient to result in about 0.01 to 5 g/l of phosphate ions.
19. The method of claim 1 wherein said surfaces are pretreated before contacting by cleaning with an aqueous alkaline cleaning solution.
20. A method for passivating lead and lead-containing surfaces comprising:
- precleaning said surface with an aqueous alkaline cleaner;
- contacting the cleaned surface with an aqueous solution of about 0.01 to 10 g/l of at least one weak carboxylic acid salt of trivalent chromium having a pH of about 2 to 6, for at least one minute and at a temperature of about 20 to 50°C;
- rinsing the contacted surface with water;
- further rinsing the contacted surface with at least partially deionized water; and - drying said surface.
- precleaning said surface with an aqueous alkaline cleaner;
- contacting the cleaned surface with an aqueous solution of about 0.01 to 10 g/l of at least one weak carboxylic acid salt of trivalent chromium having a pH of about 2 to 6, for at least one minute and at a temperature of about 20 to 50°C;
- rinsing the contacted surface with water;
- further rinsing the contacted surface with at least partially deionized water; and - drying said surface.
21. The method of claim 20 wherein said aqueous solution also contains about 0.001 to 10 g/l of phosphate ions in the form of phosphoric acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19843429532 DE3429532A1 (en) | 1984-08-10 | 1984-08-10 | METHOD FOR PASSIVATING LEAD AND LEAD-BASED SURFACES |
| DEP3429532.1 | 1984-08-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1261716A true CA1261716A (en) | 1989-09-26 |
Family
ID=6242814
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000486844A Expired CA1261716A (en) | 1984-08-10 | 1985-07-16 | Passivation of lead surfaces |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0171043B1 (en) |
| JP (1) | JPS6148575A (en) |
| CA (1) | CA1261716A (en) |
| DE (2) | DE3429532A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10400338B2 (en) | 2017-05-12 | 2019-09-03 | Chemeon Surface Technology, Llc | pH stable trivalent chromium coating solutions |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4135524C2 (en) * | 1991-10-28 | 1995-01-26 | Gc Galvano Consult Gmbh | Method and means for chromating surfaces made of zinc or cadmium or alloys thereof |
| GB9409811D0 (en) * | 1994-05-17 | 1994-07-06 | Imi Yorkshire Fittings | Improvements in copper alloy water fittings |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB118182A (en) * | 1917-10-04 | 1918-08-22 | Edwin Ebenezer Burnett | Depositing Chromium upon Metals, particularly Iron, Chemically. |
| US3592747A (en) * | 1966-08-17 | 1971-07-13 | Samuel L Cohn & Charles C Cohn | Method of forming a decorative and protective coating on a surface |
| DE2031358C3 (en) * | 1970-06-25 | 1981-10-15 | Gerhard Collardin GmbH, 5000 Köln | Process for the production of protective layers on aluminum, iron and zinc by means of acidic solutions containing complex fluorides |
| GB1461244A (en) * | 1974-06-17 | 1977-01-13 | Lubrizol Corp | Treatment of metal surfaces with trivalent chromium solutions |
| JPS57500248A (en) * | 1980-02-06 | 1982-02-12 | ||
| GB2117414B (en) * | 1982-03-26 | 1985-11-13 | Usui Kokusai Sangyo Kk | Ferrous substrates hot dip coated with lead alloy |
-
1984
- 1984-08-10 DE DE19843429532 patent/DE3429532A1/en not_active Withdrawn
-
1985
- 1985-07-16 CA CA000486844A patent/CA1261716A/en not_active Expired
- 1985-08-02 EP EP85109735A patent/EP0171043B1/en not_active Expired - Lifetime
- 1985-08-02 DE DE8585109735T patent/DE3582833D1/en not_active Expired - Fee Related
- 1985-08-08 JP JP60175628A patent/JPS6148575A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10400338B2 (en) | 2017-05-12 | 2019-09-03 | Chemeon Surface Technology, Llc | pH stable trivalent chromium coating solutions |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3582833D1 (en) | 1991-06-20 |
| JPS6148575A (en) | 1986-03-10 |
| EP0171043A2 (en) | 1986-02-12 |
| EP0171043A3 (en) | 1988-06-08 |
| EP0171043B1 (en) | 1991-05-15 |
| DE3429532A1 (en) | 1986-02-20 |
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| MKEX | Expiry |