Knowledge for the Sulphuric Acid Industry

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Materials of Construction - Saramet®
December 12, 2002

Introduction

SARAMETÒ is a high silicon containing stainless steel first introduced by Chemetics International Co. (now Kværner Chemetics) in 1982 for use in hot sulphuric acid.   The term 'SARAMET' is an acronym for "Sulphuric Acid Resistant Alloyed METal".   The use of SARAMETÒ in hot strong sulphuric acid is covered by many end use patents in several countries.  Compared to other stainless steels, the higher corrosion resistance in hot concentrated sulphuric acid is achieved by the high silicon content. 

Extensive field data has demonstrated that no significant corrosion occurs in acid velocities exceeding of 3 m/s.  Both the parent material and weld deposits exhibit this exceptional corrosion resistance.

New developments have lead to a family of materials being created by alloying the material with different elements. 

SARAMET 23Ò

The original material has been given the designation SARAMET 23Ò.   The cast version of SARAMET 23Ò is SARAMET 13Ò.

SARAMET 21Ò

SARAMET 21Ò has reduced alloy content so does not perform as well as SARAMET 23Ò, however, in some applications it can offer acceptable performance with improved ecomony.   SARAMET 21Ò is recommended for use in 98% H2SO4 at less the 95°C and in 96% H2SO4 at less the 60°C.  The material is not recommended for use below 95% H2SO4.

SARAMET 35Ò

SARAMET 35Ò was developed to be suitable over a broader range of acid concentrations, particularly in weaker acids,=.

Composition

In wrought form, SARAMETÒ has the following properties:

Chromium                                               17-18 wt%

Nickel                                                      17-18 wt%

Silicon                                                     4.5-5.8 wt%

Iron and other alloying elements                 Balance

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Weldability

SARAMET is fully weldable using gas tungsten arc welding (GTAW) and shielded arc welding (SMAW) techniques as well as PAW and GMAW.  Oxyacetylene, carbon arc and SAW cutting and welding processes are not recommended.  Special procedures are required to ensure controlled ferrite formation in the welding deposit.

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