Should pipe based structures (RHS SHS CHS) be sealed or have their ends left open? 1

[RonOz]

There are many tubular steel structures in the world. Circular, square, rectangular. Combinations of all three. Many of these structures are capped at the ends by welding a plate in place. It's commonly done. Aesthetics is one of the reasons. Another being to protect the internal surfaces from corrosion. Keeping water out will prevent rust.

The issue came up in another forum; one dominated by welders.

The notion was that tubular structures should have their ends left open, or if they are capped then drain holes should made in appropriate locations to allow water to drain from the pipes. The argument is that despite best efforts there will be pinholes in the welds or tiny gaps where the weld was not made properly, and these tiny holes will permit air to enter. Humid air will condense on the inside of the pipes and water will accumulate with the result that corrosion will take place at a faster rate than had the pipes not been sealed. The implied result is a premature failure.

The counter argument was that the welder can do a good job and the pipe is fully sealed, but if not and pinholes remain, then paint will seal any remaining problem areas. Consequently, corrosion will not be a problem as the structure is fully sealed.

What's your opinion on this?

 

[RonOz]

Thanks for the link PP. It’s an old article but still relevant, and exactly what I was looking for.

I was impressed to read that when sealed hollow sections were cut open for inspection, after such long periods of time (more than 50 years in some cases), that the internal surface often showed no sign of corrosion. I was also encouraged by evidence that where the structure was not completely sealed only slight corrosion was found, as you noted, adjacent to any holes but the remaining internal structure remained intact.

The article is in two parts. Here’s the link to part 2:

https://falconrme.com/wp-content/uploads/2019/09/Tubular-steel-vs-channel-steel-research-Part-2.pdf