CORROSION ITS

RESISTANCE

ALLOYS

OF

IN CORROSIVE

TITANIUM

AND

INDUS'TRIAL

I. I. B o n d a r e n k o , A. a n d T. M. M o z g u s h i n a

Z.

MEDIA UDC 546.821:620.193.4

Boiko,

Titanium is a p r o m i s i n g construction m a t e r i a l used s u c c e s s f u l l y in v a r i o u s b r a n c h e s of industry, including the m a n u f a c t u r e of c h e m i c a l - p r o c e s s equipment. The C h e r k a s s k ials under l a b o r a t o r y s e l e c t e d for the t e s t s denum) was t e s t e d in

Chemical Works investigated the c o r r o s i o n r e s i s t a n c e of s p e c i m e n s of titanium m a t e r and n a t u r a l conditions. In addition to technically p u r e V T I - 1 and VT1-0 titanium, also were OT-4, VT-14, 4201, and 4200 alloys. The 4201 alloy (titanium + 32% m o l y b cooperation with the State S c i e n t i f i c - R e s e a r c h Institute of the Nitrogen Industry (GIAP).

The c o r r o s i o n r e s i s t a n c e of the titanium alloys was d e t e r m i n e d g r a v i m e t r i c a l l y a c c o r d i n g to a t e n point scale. T h r e e s p e c i m e n s of each alloy were tested simultaneously in all the media. The r e s u l t s of l a b o r a t o r y t e s t s a r e given in Table 1, and r e s u l t s of industrial t e s t s in industrial units of operating shops a r e given in Table 2. F r o m the tables, it is evident that the titanium alloys a r e v e r y c o r r o s i o n - r e s i s t a n t . Thus, f o r e x a m p l e , s t a i n l e s s - s t e e l p u m p s f o r pumping acidified dichloroethane in the production of ion e x c h a n g e r s broke down a f t e r three to four months of operation, but the c a s t titanium p u m p s used now have been o p e r a t i n g s u c c e s s f u l l y since May, 1971. Since J a n u a r y , 1972, V T - l - t i t a n i u m c o l l e c t o r s for acidified dichloroethane have been used, and t h e i r condition is good. On t h e b a s i s of the t e s t s of titanium under o p e r a t i n g conditions of the ventilation s y s t e m s , V T I - 1 titanium i s r e c o m m e n d e d f o r manufacturing a i r ducts of i o n - e x c h a n g e r production shops. F r o m the r e s u l t s of the t e s t s with GIAP, it was concluded that it is n e c e s s a r y to use V T I - 1 titanium to m a n u f a c t u r e a w a s t e - g a s h e a t e r and stripping column in the n i t r i c - a c i d p r o d u c t i o n shop. Also p r o m i s i n g is the use of titanium under the o p e r a t i n g conditions of h e a t - o f - n e u t r a l i z a t i o n - u s i n g TABLE

1 9Length

Medium

Corrosion i n d e x

of tests ' in.mm/ye~r

Material

in h

58%HNO32 T e m p . 60"C

OT-4, V T I - 1 , ,VT1-0

58% H N O 3. T e m p . 80~

V_T~I4

'

L,,

80%NH4NO3 +5 g/liter HNOs. Temp. 115 ~ C NI:t4NO3 melt: 8975%NH4ND~, b. 5% H2SO4, and 10J/o H2O. T e m p . 1 4 0 150vC Acidified CaC12 solution: -52~o -- - ' 4 CaCI2, 2% HC1, and 4 6 % H 2 0 . I .r~p. 115oc I "

-

4201 .......

] ]

~

0,006

soo ,

0,043

3

Uniform film o f t e m p e r colors

~4

:Uniform l i g h t - g r a y film, uniform c o r r o s i o n

375

9 r1, 022

1

4201

348 34s,

:0,do0

0,003

2

VTI-I

6oo

0,017

4

72;

I0

34

I0

, VTI-1

VTI-1 VT1-0 4201

. 77

77

0.001S

Remark

in points

8 .

Nonunttorm corrosioE Protective

oxide

film

The s a m e

Intense dissolution, pitting corrosioll 9

Uniform corrosion

T r a n s l a t e d f r o m Khimicheskoe i Neftyanoe Mashinostroenie, No. 1, pp. 19-20, J a n u a r y , 1974. 9 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A copy of this article is available from the publisher for $15.00.

38

TABLE 2

I [ installation[ Equipment unit PlaCeof

M~t~ri,l I of te~ts }~!i J~n

Medium

rlinh 30% dichloroethane 2-3%cbloro-I sulfonic acid, 5-i:0%H2804, I 3-5%mHC1, cation exchanger, 1 .~and H20. ,rTemp. 20-I00~C t l~i'om 0 to-~36%HsSO4, dichiorol ~ [ ~thane, styrene-divinyi benzene I copolymer, and HsO. Temp. up] -~to I 0 0 ~ C 1 16.8~ NaOH, 34%ethylenediamine~ 22~cNaC1, and HzO. Temp.

"Decomposer reactor I DecomPoser reactor n Productio~ of ion ex- Reactor chart_gets Colleclora

~o ~

_

Acidified dichlorethane (up HCI). Temp. 0-25~

!:o 5%

Urea shop

Ammonia production

Dilute ni-

Temp. 170"C

o,0~

s

Speclmens' external appearance hardly changgd; uniform

corrosloN

42Ol

2780

VTI-1 I

I"

26O

[ VT1-0 [: .. vTI-I

20. 0 mg/cm s HCI and fro~-n7.5 1 to 94.9 mg/cm ~ dithloroethane,l Temp. 25"C ]

tric acid shop I Ammonium Heat-of:neutral- ] 84%NH4NO~and .2 mg/liter H N O 3

Remark

' lmm Vyea, ~omts

Specimens ~dissolqed a, durin _ g tests_ . Specimens'external 4 appearance remained |, unchanged

4200

Noxious emissions containing up to] VTI-I

Syhth~sis cohima ,Urea-ammonium carbamate melt, NH~., and H~O. Temp. 190200"C and pressure 200 atm ~Jrea solution and NHs, -CO~, an'd Distillation He0 vapors. Temp. 1602C and column 9 pmssurel7 atm i'[(egeneraior ;t" Cds-sathraied Mi~Asolution. i-~onothanolamine (MEA) Temp. 100.~C 9 solution Stripping eolmnn [ 58~oHNO~ Temp. 45~

nitrate shop ization-using unit]

928~

4201

_I

9

Ventilation-system air ducts

~176176

[ index

0,003

0,0~ 1 1 0,0015 I

I1~

0,0500 I

4752

0,0003I

f VTI-I

57~6/

VTI-I

10150

The same

Metallic luster remained (in the upper part of .thc colleetorl Specimens darkene .d ! u0d.er severe.copaitions 5 I {lnmwer part oi I _ collector) ] 'The specimens' external appearance did not change

2

Ii [C0,94I 5

The ~ecimens

were

covered with an oily _ dark-)~rownfilm

The specimens were covered with a'tempercolo_r film

VTI-I

12216

0,0005

1

VTI-i 1 3048

0,006 I 3

VTI-1 VTI-1

0,006 ]

2015 2016

90,008

The specimens were covered with a _protective oxide film ] Uniform corrosign

f 3 [ ~he same 3 I

u n i t s of the a m m o n i u m n i t r a t e shop. A f t e r 11 m o n t h s of o p e r a t i o n , titanium bubbling d e v i c e s f o r feeding n i t r i c a c i d to the h e a t - o f - n e u t r a l i z a t i o n - u s i n g units a r e in g o o d condition. U n d e r the s a m e conditions, s t a i n l e s s - s t e e l bubbling d e v i c e s b r e a k down rapidly. F o r 18 m o n t h s now, a 4 2 0 1 - a l l o y t h e r m o c o u p l e c a s i n g h a s been u s e d in the d e c o m p o s e r r e a c t o r of the c a t i o n - e x c h a n g e r p r o d u c t i o n shop u n d e r s e v e r e conditions (see Table 2, line 1), a n d its condition i s good. This i n d i c a t e s that the 4201 a l l o y can be u s e d f o r lining d e c o m p o s e r r e a c t o r s in t o n - e x c h a n g e r p r o d u c t i o n shops. The lining is now m a d e of 1~.P-496 (N70M27F) alloy, tending to u n d e r g o knife c o r r o s i o n along the weld joints. The 4201 a l l o y can a l s o be r e c o m m e n d e d f o r m a n u f a c t u r i n g p u m p s p u m p i n g an a c i d i f i e d c a l c i u m c h l o r i d e solution at e l e v a t e d t e m p e r a t u r e s . T i t a n i u m - p o w d e r - f i l l e d e p o x y r e s i n c o a t i n g s have b e e n t e s t e d s u c c e s s f u l l y in r e c y c l e cooling t o w e r s . T h e r e f o r e , t i t a n i u m p o w d e r is a good f i l l e r f o r a n t i c o r r o s i o n c o a t i n g s f o r p r o t e c t i o n a g a i n s t a t m o s p h e r i c and w a t e r c o r r o s i o n . Thus, c o r r o s i o n t e s t s and use of individual t i t a n i u m - a l l o y subunits at the C h e r k a s s k C h e m i c a l W o r k s have shown the e f f i c i e n c y a n d t e c h n o l o g i c a l expedience of u s i n g V T I - 1 and V T 1 - 0 t i t a n i u m f o r e q u i p m e n t in the p r o d u c t i o n of n i t r i c acid, a m m o n i u m n i t r a t e , i o n - e x c h a n g e r e s i n s , and u r e a , and 4201 a l l o y f o r e q u i p m e n t in i o n - e x c h a n g e r p r o d u c t i o n shops. A c c o r d i n g to p r e l i m i n a r y c a l c u l a t i o n s , i m p l e m e n t a t i o n of t i t a n i u m e q u i p m e n t will yield an a r b i t r a r y a n n u a l s a v i n g of 800, 000 r u b l e s .

39