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51317--9534-The Dilemma Found During Investigative Digs

Coatings are supposed to be the first line of defense against corrosion, while cathodic protection is secondary. Is this really occurring? The findings of direct examination digs appear to show otherwise.

 

Product Number: 51317--9534-SG
ISBN: 9534 2017 CP
Author: Joseph Pikas
Publication Date: 2017
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Due to great chemistry and metallurgical innovations of the steel industry higher strength steels have made significant strides in specified minimum yield strength (SMYS) wall thickness control toughness weight per foot etc. However one significant factor in these great improvements was no consideration for corrosion allowances. It has decreased with every incremental increase in the making of higher strength steels. Corrosion in carbon steel is the same whether it is a 35000 yield pipe or an 80000 yield pipe or 0.375” wall thickness versus 0.215” wall thickness. 25% wall loss on 35000 yield pipe results in a 44% on the higher strength steel pipe. Lower strength steel direct assessment results in recoat type repair while higher strength steel results in a composite repair or replacement. Unfortunately the US coating industry and pipeline operators have not kept up with these changes to offset or compliment the improvements in great improvements made in higher strength steel. The dilemma either add more corrosion allowances to the steel and/or improve the coatings. Coatings are supposed to be the first line of defense against corrosion control while cathodic protection is secondary.

Keywords: Specified Minimum Yield Strength (SMYS), Fusion Bonded Epoxy (FBE), Remaining Strength of Corroded Pipe (RSTRENG)

 

Due to great chemistry and metallurgical innovations of the steel industry higher strength steels have made significant strides in specified minimum yield strength (SMYS) wall thickness control toughness weight per foot etc. However one significant factor in these great improvements was no consideration for corrosion allowances. It has decreased with every incremental increase in the making of higher strength steels. Corrosion in carbon steel is the same whether it is a 35000 yield pipe or an 80000 yield pipe or 0.375” wall thickness versus 0.215” wall thickness. 25% wall loss on 35000 yield pipe results in a 44% on the higher strength steel pipe. Lower strength steel direct assessment results in recoat type repair while higher strength steel results in a composite repair or replacement. Unfortunately the US coating industry and pipeline operators have not kept up with these changes to offset or compliment the improvements in great improvements made in higher strength steel. The dilemma either add more corrosion allowances to the steel and/or improve the coatings. Coatings are supposed to be the first line of defense against corrosion control while cathodic protection is secondary.

Keywords: Specified Minimum Yield Strength (SMYS), Fusion Bonded Epoxy (FBE), Remaining Strength of Corroded Pipe (RSTRENG)

 

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