CS227469B1 - Method of electrolytic plating of objects made of materials based on iron group metals - Google Patents

Description

The invention relates to a process for the electroplating of articles of iron-based materials of metals and their alloys with nickel and its alloys from aqueous solutions.

It is a known fact that galvanic layers of nickel and its alloys, e.g. with iron, deposited from an acid bath directly on a steel, nickel or other iron-based metal alloy, exhibit low adhesion. Therefore, various more or less successful surface pretreatment techniques are currently being used to eliminate this deficiency. These include methods using, for example, copper interlayers, or technologies incorporating electrolytic pickling in baths of various compositions to remove oxide layers. All of these processes in the sequence of operations require a further electrolysis operation in a separate electroplating bath prior to the actual deposition of the desired layer. However, when rinsing and moving objects into the plating bath, an undesirable oxide layer or other surface contamination may again occur, reducing the effect of the previous operation.

The above-mentioned drawbacks are overcome by the electroplating process of the present invention intended for metallizing articles of iron-based metal materials and their alloys with nickel and its alloys from aqueous solutions. The object of the invention is that the surface of the object is first subjected to anodic pickling in the electroplating electrolyte, which is then converted into a cathodic process by rapid rewinding. According to a further feature of the invention, it is jet current

The -2 -2 density in the anodic mode ranges from 0.01 A.dm to 30 A.dm and the anodic pickling takes place from 1 s to 60 minutes.

The main advantage of the method according to the invention is a substantial simplification of the electroplating technology while ensuring the quality of the plating. By the method according to the invention, the anodically etched surface cannot be undesirably passivated again when the objects are transferred to the electrolyte of the main process. In the technological process, a special pickling bath or a galvanizing bath and the process of relocation of the metallized object, usually associated with its rinsing, are eliminated. The practical consequence is to increase the adhesion of the galvanic layer to the substrate, which makes it possible to use the plating even in thicker layers and under higher mechanical stress, eg for the renovation of machine parts or as functional surfaces of the parts.

The process according to the invention is generally carried out by suspending the pre-degreased and stained article in a plating bath, for example based on sulfosalicylan or sulphate with a complexing agent, and connecting it as an anode. The anodic current density can be chosen within the range from 0.01 to 30 A.dm ^_ 2 according to the type of the object and the duration of the anodic process, with from 1 to 60 minutes. After the required time has elapsed, changing the polarity changes the anodic to cathodic process and adjusts the cathodic current value according to the requirements of the cathodic deposition process of the metal or alloy layer. It is desirable that the polarity change be performed as quickly as possible, i.e. within 100 ms.

The electroplating process according to the invention is further elucidated by means of examples, by which the scope of the invention is not limited or exhausted.

He did

Plated steel cylinder made of low carbon chrome steel with 13% wt. ohromu

Composition of electrolyte - aqueous solution:

0,7 M nickel sulphosalicylate ί 0,1 M ferrous sulphosalicylate 0,08 M potassium iodide pH = 4,2 temperature = 50 ° C ·

The anodic pickling was performed at a current density of 1 A.dm for 5 minutes, a cathodic current density of 5 A.dm.

Example 2

Coated steel cylinder made of low-alloy chromium steel with higher carbon content and 1.5% chromium

The electrolyte composition corresponded to Example 1.

Anodic pickling was performed at a current density of 10 A.dm for 1 minute, cathodic deposition at 5 A.dm.

Example 3

Plating of chromium steel with molybdenum addition, containing 12 wt. and 2 wt.% molybdenum

The composition of an "electrolyte-aqueous solution;

0.7 lions n-kelium sulfate 0.003 M saccharin 0.05 M ferrous sulfate pH = 3.2 0.06 M sodium sulfosalicylate temperature = 50 ° C 0.08 M potassium bromide 0.5 M boric acid

(sodium salt)

The anodic pickling was performed at 0.7 A.dm ^-2 for 5 minutes. Cathodic deposition 2 at a current density of 3 A.dm.

Example 4

Plated 1 mm thick sheet of pure nickel

The electrolyte composition was identical to Example 1. The anodic pickling was performed at -2 -2

A.dm for 5 minutes. Cathodic plating at a current density of 7 A.dm.

Example 5

Plating of electrolytic nickel with nickel-tungsten alloy

Composition of electrolyte - aqueous solution:

0.8 M nickel sulfosalicylate I 0.01 M sodium tungstate

0.05 M nickel bromide pH = 4 t temperature = 50 ° C

Anodic pickling at a current density of 1 A.dm for 20 minutes. Cathodic deposition 2 was performed at 4 A.dm.

In the above examples, the plated articles were degreased with a coarse organic solvent prior to the anodic pickling process, then decoupled with Viennese lime in a 10% solution of sulfosalicylic acid in water. The deposited layers of alloys held on the substrate during machine grinding and at the edges, while the comparative samples metallized in a manner but without anodic pickling were peeled off.

Claims (2)

SUBJECT OF THE INVENTION A method of electrolytic plating of articles of iron-based metal materials and their alloys with nickel and its alloys from aqueous solutions, characterized in that the surface of the article is first subjected to anodic pickling in the electroplating electrolyte, which is then converted into cathodic by rapid polarity reversal. 2. Method according to claim 1, characterized in that the current density in the anodic mode is between 2 and 2, in the range of 0.01 A.dm to 30 A.dm, and the anodic pickling takes place from 1 s to 60 min.