DE2063735A1 - Process for the treatment of mild steel or soft iron in plates, strips or coils before processing and subsequent enamelling - Google Patents

Description

Patent attorney Dipl.-Ing. WiIh. !. instructed

84 REGENSBURG · ZOLLERSTRASSE 13 · TELEFON (0941) 53802 «« «~ ™ ο r '

20637 3b

23rd EET, J970

Regensburg, the

BRITISH STEEL CORPORATION,

London, SWl / England
33, Grosvenor Place

B 1189
L / Ma

Process for the treatment of mild steel or soft iron in plate, strip or coil form before processing and subsequent enamelling

The present invention relates to improvements relating to the treatment of mild steel, and more particularly for applying nickel to a mild steel object prior to further processing and enamelling.

The term mild steel is used in the present context for iron in plate, strip or coil form with a Carbon content of 0.15% or less.

In the earlier patent application P 20 01 750.9 was a chemical Plating bath for the treatment of steel or iron described

109823/1326

ben with the help of nickel phosphate in a concentration of 2g per liter up to 100g per liter, expressed as nickel, double sodium phosphite in a concentration of at least 2g per liter up to saturation together with free phosphoric acid in an amount between 0.1 ml and 10, 0 ml equivalent values of NORMAL sodium hydroxide. That patent application also describes the treatment of soft iron in plate, strip or coil form prior to further processing and subsequent enamelling by depositing a nickel coating from such a chemical plating bath on the soft iron body, the working temperature of the plating bath between 70 and 100 ^° C. preferably was between 80 and 90 ° C * *

It has now been found that an improved method of making the nickel coating on soft iron can be obtained if a bath, as described in the application P 20 01 750.9, is used for an electrodeposition of nickel before the Enamelling, whereby the soft iron body has already been provided with an electroless nickel coating beforehand.

According to the present invention is a method for treatment of soft iron in plate, strip or bobbin shape " provided before processing and subsequent enamelling, in which on the soft iron body initially an electroless Nickel coating is generated, whereupon the soft iron body thus coated as the cathode in an electroplating circuit

1093 28/1328

is switched on with any anode and the electrolyte is a bath containing nickel phosphate in a concentration of 2g per liter up to 100g per liter, expressed as nickel, double sodium hydrogen phosphite in a concentration of at least 2g per liter until saturation, together with free phosphoric acid with an amount between 0.1 ml and 10.0 ml equivalent to NORMAL sodium hydroxide and using a current of 10 to 1000 A per square foot (1 - 100 A / qm) cathode area and a bath temperature between 0 and 100 ⁰ C.

The anode is preferably made of nickel or a chemically neutral one Substance, in particular made of a substance that is not attacked electrolytically, such as stainless steel or graphite.

The formula for nickel phosphate can be given as Ni ₃ C PO ₁ ^) ₂ ⁴ XH ₂ O, where X is between * and 8, preferably 7 and 8.

The preferred concentration of the nickel phosphate is between 10 and 25 g per liter, expressed as nickel. The concentration of the nickel phosphate can expediently be determined by Titration with N / 10 double sodium salt of ethylene-diamine-tetra-acetic acid using "murexide" as an indicator in an ammonical solution ("murexide" is an ammonium salt of purple acid). However, any conventional analytical technique can be used for monitoring the concentration of the nickel phosphate be used.

109828/1326

While a concentration of double sodium iPtoospels of only 2g per liter is quite useful, it is preferred to use a concentration of 10 to 50g per liter »Me monitoring this component can be done by back titrating excess Iodine with H / 10 sodium IMo-sulphate "solution in one Reagent vial with buffered pH between 6 and 8. The solution is left in the dark with excess iodine for an hour before back titration with sodium thio-sulphate. However any other analytical technique can also be used. The concentration of free phosphoric acid in the electrolytic Flaking solution can be determined by any appropriate analytical technique, e.g. B. Titration with WORMÄL caustic soda »

The preferred concentration range is between 0.15 ml and 0.25 ml NORMÄL caustic soda equivalence »

While the working temperature of the bath for electron leather impact of nickel can be in the wide range from 0 to 100 ^, however, the preferred working temperature is 80 to 90 ⁰ C or 85 to 87 ° C.

When preparing the electrolytic bath, 4as nickel phosphate can be used initially as such and in the same way In the necessary fillers are supplied, as indicated by analysis of the Plating bath appears, it can also be in the form of Nickel phosphate or In both cases, the nickel can also be in, form

ORIGINAL INSPECTED

■■ - - 5 - ^;

of nickel carbonate, nickel hydroxide, or any combination
of which are added in order to bring the nickel phosphate concentration to the desired value by reacting with dissolved phosphoric acid in the bath. I.

Any electroless plating baths can be used in the first \ treatment stage in accordance with the invention,
e.g. any burner-type nickel cation hypophosphite anion plating; rungsbad, including those as described in an earlier patent are [ben, but a chemical plating bath of the type can be more conveniently described in the Application No. P 20 01 750.9.

The use of an electric current for precipitation
of the nickel from the described electroplating bath accelerates the deposition rate of the nickel and considerably
gives a less porous coating than the precipitate of
electroless nickel, but the adhesion and appearance of the
Enamel favors. It is an advantageous feature of the method according to the invention that the ratio of electroless
Nickel to electron hammered nickel within wide limits
can be changed. The procedure provides a complete
Plating within the range of 20 to 250 mg nickel each
Square feet (0.2-25 mg / m2) of the iron body.

10982 87 132 6

The following three examples illustrate the inventive; moderate procedures in which the same bath in both plating | steps, ie electroless and electrodeposition of nickel, | is used. ]

• Example 1:
! A bath is made using

Ni (CO ₃ ) .Ni (OH) ₂ .IfH ₂ O 50 g / l

5H ₉ O 30 g / l

free H ₃ PO ₁₊ 2.5 ml equivalent N.NaOH

N = normal

The temperature of this bath was maintained at 85 ° G and for the electrodeposition stage the anodes were made of stainless Stole. The current used was 50 amps per square foot (5 amps per square meter). The soft iron sample was immersed in the immersed the above bath to obtain the electroless plating and then turned on the power for 18 seconds to disconnect the Generate electronxedge strike.

Example 2:

The bathroom consisted of

Ni (OH) ₂ 23 g / l

NaHPO ₃ 5H ₂ O - 20 g / l

free H ₃ PO ₁₊ 2.0 ml equivalent N.NaOH

109828/1326

The temperature of this bath was kept at 87 ° C and Mr die Electron precipitation stage uses a graphite anode »A Current of 100 amps per square foot <10 A / qm) was used and a test piece of soft iron in the mentioned bath for IB seconds immersed in order to obtain the electroless coating and then switched on the current for 9 seconds to prevent the electrodeposition to obtain,

Example 3:

The bathroom consisted of

₃ ^) ₂ , 8H ₂ O 58 g / l

NaHPO ₃ 5H ₂ O. 25 g / l

free H ₃ PO ₁ ^ 2.5 ml equivalent N.NaOH

The temperature of this bath was kept at 87 ° C and for the Electron precipitation stage used as anode nickel. A stream of 75 A per square foot (7.5 A / m2) was used and the soft iron body immersed in the bath for 12 seconds to obtain the electroless coating and then switched on the power for 12 seconds, to get the electrical precipitate.

109 828/1326.

Claims (3)

Claims 1. Process for treating soft iron in plates, strips or Coil shape before further processing and subsequent Enameling using a deposit on the Soft iron body in the form of an electroless nickel coating with subsequent use of the soft iron body coated in this way as a cathode in an electroplating circuit with some anode and an electrolyte bath of nickel phosphate in a concentration of 2 to 100g per liter, expressed as nickel, double sodium phosphite in one Concentration of at least 2g per liter up to saturation together with free phosphoric acid in a range between 0.1 up to 10.0 NORMAL sodium hydroxide equivalence and thereafter Switching on a current between 10 to 1000 A per square foot (1 - 100 A / sqm) cathode area, whereby the bath temperature is between 0 and 100 C. 2. The method according to claim 1, with an anode made of nickel or another chemically inactive substance, and in particular one Substance that is not attacked by the electrolytic solution. 3. Process according to Claims 1 and 2, characterized in that the nickel phosphate concentration is between 10 and 25 g per liter expressed in nickel. 109828/1326 1. The method according to claims 1 to 3, characterized in that that the sodium phosphite concentration is between 10 and 50g each Liters. S. Method n * ch d «n claims 1 bit H, characterized in that tftft 4it Ti» tt * fttur 4 ·· M4 ·· fttr 4en Elektroniede rieh lag de · \ Nickel between 10 and 90 ⁰ C, vc & ugeweis · 85 bit 87 ⁰ C, is located. 109828/1326