Semi-Bright Nickel Plating Bath and Method of Using Same

Abstract

A nickel plating bath for plating a semi-bright nickel deposit on a substrate comprising a) nickel sulfateions; b) a soluble salt of chloroacefic acid, acetic acid, glycolic acid, proprionic acid, benzoic acid, salicylic acid or chlorobenzoic acid; and c) at least one diol selected from the group consisting of hexyne diol, butyne diol and combinations of the foregoing. The semi-bright nickel plating bath described herein produces sulfur-free semi-bright deposits over a very wide current density range. The plating bath described herein is at least substantially free of coumarin and produces desirable leveling characteristics. The bath also requires no aldehydes to achieve simultaneous thickness and electrolytic potential (STEP) and has extremely low stress and excellent ductility.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a continuation-in-part of U.S. application Ser. No. 12 / 620,746, filed on Nov. 18, 2009, the subject matter of which is herein incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates generally to semi-bright nickel plating baths that provide good properties with respect to leveling, ductility and stress and that are virtually sulfur-free.BACKGROUND OF THE INVENTION[0003]Bright nickel plating baths are used in the automotive, electrical, appliance, hardware and other industries. The most important functions of bright nickel plating are as an undercoating for chromium plating, helping finishers achieve a smooth bright finish and providing a significant amount of corrosion protection.[0004]For decorative plated parts that need a high level of basis metal corrosion protection, semi-bright nickel deposits are almost always used in conjunction with subsequent deposits of brig...

AI Technical Summary

Benefits of technology

[0018]It is an object of the present invention to provide a highly leveled semi-bright nickel deposit with excellent ductility and very low stress.

[0020]It is another object of the present invention to provide a semi-bright nickel plating bath that does not require aldehydes to provide acceptable simultaneous thickness and electrolytic potential (STEP) results.

[0021]It is still another object of the present invention to provide a semi-bright nickel plating bath that provides good stability over the life of the bath.

Problems solved by technology

Highly compressed deposits can result in blisters, warping or cause the deposit to separate from the substrate, while deposits with high tensile stress can also cause warping in addition to cracking and reduction in fatigue strength.

However, such characteristics are short-lived, because such high coumarin concentrations also result in a high rate of formation of detrimental breakdown or degradation products.

These degradation products are objectionable in that they can cause uneven, dull gray areas that are not easily brightened by a subsequent bright nickel deposit, they can reduce the leveling obtained from a given concentration of coumarin in the plating bath, and they can reduce the beneficial physical properties of the nickel deposits.

It has also been suggested to reduce the concentration of coumarin in the bath in order to reduce degradation products and thus increase bath life, but such reduction in coumarin concentration is often accompanied by a loss of leveling and also makes the bath more sensitive to degradant build-up.

However, the use of such additives has certain limitations because even moderate concentrations of these materials not only increase the tensile stress of the nickel electrodeposits, but also significantly reduces the leveling action of the coumarin.

Another problem with coumarin is odor.

The amount of coumarin required for a plating bath produces an offensive odor that can irritate eyes and mucous membranes.

However, to date, none of these baths formulations have met all of the necessary criteria.

As explained above, while the leveling of coumarin is exceptional, coumarin has a disagreeable odor, breaks down and forms harmful degradation products, and these degradation products can only be removed by batch carbon treatments of the plating bath.

These treatments are expensive and time consuming and normally must be done at least monthly and in some cases, even weekly.

In addition, none of these baths level nearly as well as a full coumarin system.