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Electrolytic passivated tin plated steel

Inactive Publication Date: 2010-07-22
BIBBER JOHN W
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006]My invention eliminates the need for hexavalent chromium and / or trivalent chromium compositions which, due to their extreme toxicity, are being removed from the work place environment. In addition my process will provide the same level of sulfide stain resistance and coating adhesion as the chromium based compositions. At the same time this process is less expensive and requires no toxic waste disposal.
[0008]Various other materials may be added to these solutions to act as wetting agents, increase conductivity, control the PH (buffers) or prevent biological attack as long as these materials do not act to prevent the reaction of the steel and / or tin with the materials in the solution in question. The distribution of the tin on tin plated steel, the uniformity of its thickness and its corresponding density will differ from one batch of tin plated steel to another as will the iron. As an example, Tin plated steel with a “matt” finish will have a greater surface area and as a result more non uniformity in the distribution of tin over the surface of the tin plated steel. As a consequence the distribution of phenolic acid salts and / or hydroxyl organic acids salts will of necessity differ from one batch of tin plated steel to another. We find that we are able to obtain more consistent overall results by the addition of phosphates, silicates and aromatic acid salts to our hydroxyl organic acid compositions.

Problems solved by technology

Below 5.0 grams per liter it is not economically feasible to deposit these materials in sufficient quantity for them to be effective in preventing sulfide stain resistance or to improving the adhesion of the tin plated steel surface.
Coil coating lines used to plate out tin on steel will generally not allow for more then about five seconds of exposure to any given electrochemical cell used to passivate the tin plated steel.
As an example, Tin plated steel with a “matt” finish will have a greater surface area and as a result more non uniformity in the distribution of tin over the surface of the tin plated steel.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 2

[0014]A five percent solution of hydroxyl acetic acid was added to a 0.5% solution of food grade hydrolysable tannic acid and the PH of the mixture was then adjusted to a PH of 9.0 by the addition of potassium hydroxide. This solution was then used in an electrolytic cell in which the tin plated steel was made the anode and a high grade stainless steel panel was used as the cathode. 7.5 volts and a current density of about 50 amps per square foot were passed through the cell for three seconds. The tin plated steel panel was then removed, rinsed in D.I. water, dried and then placed in a 0.6% cysteine solution adjusted to a PH of 7.0 by the use of tri sodium phosphate and boiled for one hour to remove all oxygen in accordance with testing procedures outlined by “Mittal Steel USA”. The outer tin layer did not yellow after one hour of exposure to the sulfide staining solution indication that a hydroxyl organic acid was needed to passivate the tin.

example 3

[0015]A six percent solution of hydroxyl acetic acid and 0.5% phthalic acid was adjusted to a PH of 9.0 by the addition of potassium hydroxide. This solution was then used in an electrolytic cell in which the tin plated steel was made the anode and a high grade stainless steel panel was used as the cathode. 7.5 volts and a current density of about 50 amps per square foot were passed through the cell for three seconds. The tin plated steel panel was then removed, rinsed in D.I. water, dried and then placed in a 0.6% cysteine solution adjusted to a PH of 7.0 by the use of tri sodium phosphate and boiled for one hour to remove all oxygen in accordance with testing procedures outlined by “Mittal Steel USA”. Within a five minute period of time, the outer edges of the panel became a dark black which then spread to the rest of the panel while the outer layer of tin remained silvery in color and then began to slowly turn yellow in color. An analysis to the panel showed the presence of a thi...

example 4

[0016]A five percent solution of hydroxyl acetic acid was added to a 0.5% solution of food grade hydrolysable tannic acid and the PH of the mixture was then adjusted to a PH of 9.0 by the addition of potassium hydroxide. This solution was then used in an electrolytic cell in which two tin plated steel panels were made the anode and a high grade stainless steel panel was used as the cathode. Seven point five volts and a current density of about fifty amps per square foot were passed through the cell for three seconds. The tin plated steel panels were then removed, rinsed in D.I. water and dried.

[0017]One of tin plated panels was placed in an oven at 400 degrees F. for thirty minutes in accordance with testing procedures outlined by “Mittal Steel USA”. The panel showed no traces of yellow tin oxide.

[0018]The second tin plate panel was first rinsed with a one percent hydroxyl acetic acid solution to remove any unwanted alkalinity and then coated with “Valspar 6256054 GLDEPOXY” accordin...

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Abstract

An electrolyte composition for passifying tin plated steel wherein the essential ingredient consists of a mixture of organic hydroxyl acids and phenol organic acids; a method of passifying tin plate steel articles with the composition by electrolysis with a pH of about 7.0-10.0 and preferably a pH of 8.0-9.5; and providing the passified tin plated steel article produces by the method along with the passified articles having an appropriate paint thereon.

Description

FIELD OF INVENTION[0001]This invention relates to an electrolytic coating composition for tin plated steel articles which provides the tin plated steel with a protective coating and improved paint adhesion.[0002]More particularly, the present invention provides a tin plated steel coating composition having as its essential ingredients organic hydroxyl acids, both saturated and unsaturated, and phenol organic acids; the method of coating the surface of the tin plated steel articles; and the tin plated steel article electrolytically coated with the composition having as its essential ingredients organic hydroxyl acids, both saturated and unsaturated, and phenol organic acids; and the coated articles painted.BACKGROUND OF THE INVENTION[0003]The natural oxide film on a tin plated steel surface provides a protective barrier and acts to improve paint adhesion. Maintaining this oxide film while at the same time preventing the rapid and uncontrolled growth of the oxide to a thick, yellow an...

Claims

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Application Information

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IPC IPC(8): C25D7/00C25D5/36
CPCC25D5/36C25D11/34C25D5/48
Inventor BIBBER, JOHN W.
Owner BIBBER JOHN W
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