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Cleaning of SS pipes

After welding of small diameter of SS pipes we notice the HAZ black in colour. External side we go for pick/passivation. Is there any solution for internal cleaning where areas are not reached manually? or any other solution to avoid this black colour on internal sides of ss pipes.

Sreenath
gatewall - Abudhabi, UAE
2006

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First of three simultaneous responses --

Use an inert gas purge inside the pipes during welding. Avoid pickling the insides; it roughens surfaces and is very difficult to inspect. Clean and passivate the insides by pumping solutions & rinsewater. Blow dry with clean air. ASTM A380 gives useful information.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2006

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Second of three simultaneous responses --

Setting up a slow purge of nitrogen or preferably argon thru the tube will significantly reduce the black oxide formed.

James Watts
- Navarre, Florida
2006

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Third of three simultaneous responses --

Purchase specification ASTM A967 and recommended practice ASTM A380 and take you pick from multiple methods of cleaning up your welds.

Joseph Lockrem
- Indianapolis, Indiana, USA
2006