US2266430A - Etching solution - Google Patents

Description

Patented Dec. 16,

UNITED STATES .PATE

T OFFICE E'TonrNG -;SOLUTION Irving C. Matthews, Rochester, and Gordon B.

Hanneman, Syracuse, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 1, 1939,.

- Serial No. 276,868

1 Claim.

, (Cl. 4-1-42) This invention relates to solutions for etching T invention to provide a solution which will give these highly desirable results stainless steel.

It is well known that stainless steels of the 18-8 or other types are much more resistant to when used with corrosion than ordinary steels. They .are, therefore, more diiiicult to etch to any great depth. Ordinary etching solutions are not sumciently rapid in their attack to be practical when, etching stainless steel to a considerable depth. Furthermore, it is diflicult to get a solution which is non-selective, i. e. which attacks each component of the metal equally and thus produces a uniform etch.

According to the present invention, an etching .solution having the above desirable properties is made up comprising: ferric chloride, nitric acid, hydrofluoric acid.

That is, we have found that the addition of hydrofluoric acidto the materials commonly used for etching, makes the solution satisfactory for etching stainless steel, whereas no previously known material would give satisfactory results. In practice, we make up thesolutions containing these materials from saturated ferric chloride claim.

solution (e. g. 91.8 grams of ferric chloride in 100 grams of water at 20 centigrade), concentrated nitric acid (specific gravity 1.42) and commercial hydrofluoric acid (48% HF i. e. approximately 50% H1?) We have found that'the most efficient concentrations of these materials are by volume as follows:

' I Parts Saturated ferric chloride solution '4 Concentrated nitric acid 1 Commercial hydrofluoric acid 1 Of course, concentrations slightly different from these give satisfactory results and even other materials may be added, but'we have found that if the solution contains between 25 and 75% saturated'ferric chloride, between 10 and 50% concentrated'nitric acid and between 10 and 50% hydrofluoric acid, it is quite useful for etching stainless steel printing rollers. centrations are by volume.

Having thus described the preferred embodiment of our invention, we wish to point out that it is not limited to the specific concentrations mentioned, but is of the scope of the appended These con- What we claim and desire to secure by Letters Patent'of the United States is:

An etching solution comprising approximately 4 parts by volume saturated ferric chlorid solution, 1 part byvolume concentrated nitric acid and 1 part by volume of a 50% aqueoussolution of hydrofluoric acid.

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