| Search our quarter-million Q&As |
Home of the finishing HOTLINE since 1989
-----Flattening the ends of steel tubes leads to corrosion?
avail from AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
(as an Amazon Associate & eBay Partner, we earn from qualifying purchases)
Quickstart:
Flattening or otherwise cold forming of steel introduces stresses, and stress points are anodic to non-stressed areas and will tend to sacrificially corrode, although phosphating will tend to neutralize these hot spots to the point where it is generally not a serious problem.
Proper pretreatment of steel is crucial to its corrosion resistance, and phosphating is the usual pretreatment. Without phosphating adhesion will suffer, these anodic hot spots will start to corrode, and underfilm corrosion (corrosion under the paint or powder coating) will develop.
for Shops, Specifiers, & Engineers
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
(as an Amazon Associate & eBay Partner, we earn from qualifying purchases)
Q. We are working with some tubular structure designs. I have been told that flattening ends of MS tubes which are then powder coated tends to have corrosion due to moisture having entry points at the ends of tube. We then get corrosion leeching out from the ends in (outdoor product) the rains making things ugly apart from the obvious corrosion. This is a consumer product so aesthetics are key factor. Our powder coats have a CED
⇦ huh? base.
Given that this is such a commonly used, cheap and effective way to make tubular products I was wondering what the general consensus in the industry is with this issue? ⇦ Answer?
- UK
September 11, 2019
for Shops & Engineers
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from eBay, AbeBooks, or Amazon
avail from AbeBooks, or Amazon
avail from AbeBooks, or Amazon
(as an Amazon Associate & eBay Partner, we earn from qualifying purchases)
A. Hi Roy. Moisture accumulation & entrapment are certainly a corrosion issue, and this is somewhat amplified by the fact that the stressed metal is anodic to the rest of the tube, tending to sacrificially corrode. I think the best answer (in addition to designs which discourage water from getting in and encourage it to get out) is proper zinc phosphatization, plus your e-coating before powder coating.
I bought a backyard gazebo/screen tent constructed with such flattened end tubing and it was rusting in under a week, so I appreciate the issue.
opinion! However, my strong suspicion is that no attention had been given to proper phosphate pretreatment -- especially because there is zero environmental pressure towards sustainability and making metal fabrications durable, but enormous pennywise/pound foolish environmental pressure towards harassing finishing shops to reduce pretreatment chemical usage, and sabotaging their sustainability efforts.
If the tubes are immersion phosphatized (so there is some coverage on the I.D., e-coated, and powder coated, I think they will last a good while without corrosion.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.