CATHODIC PROTECTION IN CARGO TANKS-DOES IT WORK?

Although sacrificial anodes will protect a cargo from corrosion, it should not be assumed that, because sufficient anodes are fitted, the tank will be free from corrosion; conditions necessary for optimum protection are hard to achieve, and at best the corrosion will be reduced by about 80% compared with a tank without anodes. Various tank conditions require different considerations in respect of both anodes and tank coatings, and the Author (of B.P. Tankers) discusses these, for both crude-oil and clean-oil carriers, under the headings:--(a) Crude-oil/clean-ballast tanks; (b) Crude-oil/empty-but-washed tanks; (c) Crude-oil/dirty-ballast tanks; (d) Clean-oil/clean-ballast tanks; (e) Clean-oil/dirty-ballast tanks; (f) Salt-water ballast-only tanks. The effect of inert gas on pitting inside tanks is also discussed. The Author's Company is still studying this matter, but present opinion is that the effect is very small. Neither impressed-current cathodic protection, nor magnesium sacrificial anodes, are allowed in cargo-oil tanks, and there are height restrictions if aluminium anodes are used. B.P. Tankers therefore use only high-purity zinc sacrificial anodes. The paper includes some information on the company's practice in inspecting the condition of the tank steelwork and the anodes. The cost of the provision and periodic replacement of anodes is much less than the cost of steel renewals in unprotected tanks. The paper includes some comparative data on these costs. Order from BSRA as No. 51,653.

  • Supplemental Notes:
    • From ISPCC78, April 1978, Part 1, Pre-Conference Manual (p 47).
  • Corporate Authors:

    Third Int'l Ship Painting & Corrosion Conf & Exbn

    Monte Carlo,   France 
  • Authors:
    • Hassan, N
  • Publication Date: 1978

Media Info

  • Pagination: 2 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00303328
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Report/Paper Numbers: Conf Paper
  • Files: TRIS
  • Created Date: Feb 27 1980 12:00AM