Resistencia a la corrosión del acero revestido con Ni autocatalítico en medios alcalinos

 

Miguel Sánchez,^1,* Henry Orozco,²Orlando Pérez¹

 

¹Centro de Estudios de Corrosión, Universidad del Zulia, Venezuela

²Universidad Nacional Experimental Rafael María Baralt, Venezuela

 

Received 25 April 2008; accepted 14 January 2009

 

Resumen

El niquel 200 es utilizado en la industria petroquimica, en el manejo de disoluciones causticas, en una variedad de componentes y equipos fabricados con materiales altamente resistentes a la corrosion. Sin embargo, dado su alto costo y la incidencia de fallas por corrosion, es necesario recurrir a otros materiales alternativos que puedan mitigar este fenomeno. Uno de ellos es el acero revestido mediante niquel fosforo electroless (sin paso de corriente), el cual en algunas situaciones y bajo ciertas condiciones ofrece alta resistencia. El objetivo de este trabajo fue evaluar la resistencia a la corrosion de probetas de acero recubiertas por niquel electroless (EN), en diferentes concentraciones de sosa caustica y establecer el espesor de recubrimiento optimo correspondiente a cada concentracion de NaOH. Los resultados de los analisis quimicos realizados por EDX indicaron que la composicion de los revestimientos EN fosforo corresponde a 10,5 % de fosforo y 89,5 % de niquel con durezas promedio de 550 HV. La velocidad de Corrosion para el acero EN estuvo en el orden entre 10,0 y 13,6 ƒÊm/ano (25 oC) y 10,2 y 14,7 ƒÊm/ano (85 oC). Mientras que para el niquel 200 estuvo en el orden entre 4,7 y 5,2 ƒÊm/ano (25 oC) y 7,0 y 9,9 ƒÊm/ano (85 oC). Comparativamente, el niquel 200 resulto mas resistente a la corrosion que el acero revestido mediante EN, pero su costo es mas elevado.

Palabras clave: electroless Ni, niquel 200, disoluciones alcalinas, corrosion,

 

The Corrosion Behavior of Electroless Nickel-Coated Steel in Alkaline Solutions

Abstract

Nickel 200 is used in the petrochemical industry in the handling of caustic solutions using a variety of components and equipments made of materials highly resistant to corrosion. However, due to their high costs and their impact on failures by corrosion, it is necessary to resort to other alternative materials that could mitigate this phenomenon. One of them is steel coated with electroless nickel (without passing flow), which in certain situations and under certain conditions offers high resistance. The aim of this study was to evaluate the corrosion resistance of the coated steel test coupons by electroless nickel (EN) in different concentrations of caustic soda and establish the optimal coating thickness for each concentration of NaOH. The chemical analysis conducted by EDX indicates that the composition of coatings in phosphorus compounds are phosphorus by 10.5% and 89.5% nickel with hardnesses average of 550 HV. The corrosion rate in steel EN was in the order between 10.0 and 13.6 mm/yr (25 °C) and 10.2 and 14.7 mm/yr (85 ° C). While for nickel 200 it was in the order between 4.7 and 5.2 mm/yr (25 °C) and 7.0 and 9.9 mm/yr (85 °C). Nickel 200 was comparatively more corrosion resistant than steel coated with electroless nickel, but its cost is higher.

Keywords: electroless Ni, nickel 200, caustic solutions, corrosion.

 

Texto disponível em PDF

Full text only in PDF format

 

References

1. R.N. Duncan, Performance of Electroless Nickel Coatings in Oil Field Environments, CORROSION/82 Conference, National Association of Corrosion Engineers, Houston, March 1982.

2. R. Parkinson, Properties and Applications of Electroless Nickel. Nickel Development Institute, NiDI Technical Series No. 10081.

3. M. Sánchez, J. Zambrano, O. Pérez, J. Podestá, Electroless Ni Coating Used in 4% NaCl Corrosion Control of Mild Steel, CORROSION 97 NACE International, New Orleans- Louisiana - USA. 1997, Paper N° 433.

4. M. Castro, B. Ana, Evaluación de Revestimientos Metálicos y no Metálicos Resistentes a la Corrosión en servicio de Agua del Lago de Maracaibo, Tesis de Maestría, LUZ. Facultad de Ingeniería, Maracaibo, 2002.

5. ASTM B-733, Standard Specification for Autocatalitic Electroless Nickel Phosphorus Coating on Metal.

6. ASTM B-578, Test Method for Microhardness of Electroplated Coatings.

7. ASTM G-59, Practice for Conducting Potentiodynamic Polarization Resistance Measurements.

8. ASTM G-61, Conducting Cyclic Potentiodynamic Polarization Measurements for Local ized Corrosion Susceptibility on Iron, Nickel, or Cobalt based Alloys.

9. ASTM G-102, Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements.

10. NACE International Publication GA287, Electroless Nickel Coatings, 1997.

11. R.P. Tracy, G.J. Shawhan, Practical Guide to Using Ni-P Electroless Nickel Coatings, Materials Performance, July 1990.        [ Links ]

 

* Corresponding author. E-mail address: miguelcvc@yahoo.com