NEW MATERIALS AND CORROSION CONTROL

INVESTIGATION OF THE CORROSION RESISTANCE OF VITREOUSENAMEL COATINGS IN FORMIC-ACID-MANUFACTURING MEDIA UDC 620.193:666.293.52

P. S. Shkolyar, A. P. Manzhelii, O. V. Bobovich, and T. P. Borodai

in the Scientific-Research Institute for Enameled Chemical-Machinery Manufacture, investigations were carried out on the corrosion resistance of vitreous-enamel acid- and alkali resistant coatings UES-300 and 5-Ts and acid-resistant coating 261 in some media of an advanced technological process for the manufacture of formic acid from carbon monoxide and water. Enameled specimens with diameter 85 mm and thickness 3 mm were tested under laboratory conditions in solutions of methanol, formic acid, and methyl formate and in mixtures of formic and acetic acids and toluene at 80 and 100~ for i00 h with changes of the solution every i0 h. The test results and the maximum permissible service temperatures for the tested coatings, which were calculated on their basis, are given in Table i. As is evident, the durability of the tested coatings in aqueous solutions of methanol, formic and acetic acids, and toluene was rather high (0.004-0.02 mm/yr). Under the mentioned test conditions, leaching of the coatings in methyl formate was not observed. Under pilot-plant conditions, the coatings were investigated on cylindrical specimens assembled on a dowel in pairs with Ftoroplast (Teflon) spacers. The specimens were hung on a Ftoroplast strip in equipment and tested for i000 h in media of the following compositions (%): 30-40 methyl formate, 10-15 methanol, 15-21 formic acid, and water (temperature T = II0~ and pressure p = 0.6 MPa); 30-40 formic acid and 60-70 water (T = 80~ and p = 0.05 MPa); 3 formic acid and 97 water (T = I14~ and p = 0.08 MPa); 20-30 methyl formate and 70 TABLE 1 M a x . service

Coating

temp. (~ at the permissible corrosior~ rate, ram/yr

Medium

0,5

0,2

0, 1

11o0 0,0340,03910,0130"011 187 182 0,036 0,012 184

158 160

162

145 141 143

5-Ts 261

0,048/O,Ol0 t 176 100 0,036 0,012[ 184 0,043 0,015 178

153 I00 155

137 144 138

U~S-30( 50% formic acid 5-Ts 20~

100 0,02 10,007

UI~s-a005.Ts11% formic acid 261

U~S-300 10% formic acid

U~S-300 5-Ts 1%o methanol

~61

U~S-30C 5-Ts

0,05 ]0,017 0,034 0,0li

o,o13 0,005 0,04

174 15i 135 199 173 156 167 162 146 I63 146 130 159 138 123

solution

80 0,016

0,021 0,007

149

129

120

15% m e t h a n o l

0,026 [ 0,009 60 o,o31 o,oi 0,04 0,013

159

138 136 138

123 123 123

261

solution

U~S-30s 5-Ts 261

98% methyl formate solution

60

159 I58

Leaching not observed

/ UES-300! 20% formic acid + 80% toluene 0,034 0,011I 173 150 solution I 9o 80% formic acid + 20% toluene 9o 0,051t0,017/ 16] 139 solution 90% formic acid + 0.03% toluene lOO 0,07 I0,02 ] 170 148 solution + 1% acetic acid + water

I

135 124 132

f

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 12, p. 28, December, 1987.

0009-2355/87/1112-0623512.50

9 1988 Plenum Publishing Corporation

623

methanol (T = -6 to -10~ and p = 0.05 MPa); 98 methyl formate and 2 water (T = 30~ 0.i MPa); and 3 formic acid and 97 water (T = 15-20~ and p = 0.i MPa).

and p =

The corrosion resistance was evaluated by visual examination of the surface condition and investigation of the uniformity of the coatings with an IDS spark defectoscope with a voltage of 12 kV. It was found that the coatings had high corrosion resistance in all the experimental media. The quality of the coatings did not change, and the surface of the specimens retained its original brightness and uniformity. Thus, vitreous-enamel acid- and alkali-resistant coatings UES-300 and 5-Ts and acidresistant coating 261 can he recommended for the protection of equipment operating in some formic-acid-manufacturing media.

EXPERIENCE IN THE INTRODUCTION OF A POSITIVE PHOTORESIST IN THE PRODUCTION OF NICKEL SCREENS BY THE GALVANOPLASTIC METHOD UDC 664.1.038.2:621.928.028.3

L. V. Egorova and I. M. Davydova

In the sugar industry and for clarification of fruit and vegetable juices in the preserving industry, continuous action inertial centrifuges are used. Their filtering elements are 0.22-0.25-mm-thick nickel screens prepared by the galvanoplastic method with round and slit-shaped holes with a diameter or width of 0.05-0.09 mm. Previously, a negative photographic lacquer based on polyvinyl alcohol was used in the production of such screens [i]. At present new light-sensitive materials, among which a leading place is occupied by orthonaphthoquinone diazides, have been developed [2]. These materials serve as the basis of a whole series of photoresistors produced by industry and possessing valuable technical properties including the ahsence of nonexposed hardening, high light sensitivity, solubility in nontoxic organic solvents, and the capacity to form acid resistant films with good protective properties. The purpose of this work was an investigation of the possibility of use of light sensitive materials based on orthonaphthoquinone diazides for selective protection of matrices of 12KhI8NIOT steel during protection of nickel screens by the galvanoplastic method. The conditions of application of the photoresist, development, and hardening were selected based on the quality of the image of the picture, the color, and the condition of the photoresist and also on the quality of the screens grown in nickel plating sulfamine electrolyte. The photoresist was applied on a matrix of 12KhI8NIOT steel by the drawing method. The results of the investigation showed that in the as-received condition the selected photoresist may not be used in the production of nickel screens as the result of the fact that a coating of significant thickness obtained on the matrix is processed poorly in the operations of copying and development. A thin uniform layer and a good quality screen were obtained with addition to the photoresist of a diluent to a viscosity of 2 min 30 sec. In selection of the composition of the solution for development of the image on the photoresist it was established that in solutions of 20 g/liter of trisodfum phosphate, 20 g/liter of calcined soda, and 20 and 40 g/liter water glass the pictures do not develop and in a number of cases the copying layer fails during development. In a 6.6 g/liter NaOH solution the developing time is a minimum but it rapidly loses its developing properties, the developing time increases by 1.5-2 times, and the coating starts to fail. The best results were obtained in a solution containing 4 g/liter of NaOH and i0 g/liter of water glass. In this solution development occurs more slowly than in a solution of 6.6 g/liter of NaOH. The copying layer does not fail even with a significant increase in development time. Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 12, p. 29, December, 1987.

624

0009-2355/87/1112-0624512.50

9

1988 Plenum Publishing Corporation