HVOF/TSA Coating -vs- Special Paint/Coating System

[takiyasamsama]

Hi,

In comparison between HVOF/TSA coating and painting, I need to know is there any alternatives to HVOF/TSA like using special painting/coating system?

I see that HVOF/TSA is the ultimate solution when dealing stress corrosion chloride (SCC) when applied on carbon or stainless steel body. Yes, I mean it, STAINLESS STEEL, because our client/customer specifications mentions that 316L is not permitted for operating temperatures above 60 centigrade, hence they insist to coat the stainless steel body using HVOF/TSA.

My main idea and concern is, can we use special paint/coat system as an alternative to HVOF/TSA? For example what we had in mind (me and my supplier) is that we use paint from International® Paint, called Intertherm 50 with Interzinc 22 undercoat or Intertherm 751.

Appreciate anyone with experience of the same situation to share with me and others, if this alternatives is acceptable?

Regards

 

[cap1a79]

The reason why TSA coating is preferred for insulated piping is due to that insulated pipe is invisible so visual inspection is not feasible to check conventional coating that has limited design life (mostly 5-15 years maximum) and not free from coating defect and water permeation for old coating. Furthermore, if the pipe is SS, external SCC will be another issue that could happen only for short period of time (not time dependent corrosion but "crack")
Due to the above reason, TSA is kind of common covering the above. If you consider coating other than TSA, at least, the design life shall cover sufficiently for expected lifetime of the plant without maintenance or invasive removal of the insulation.(not equal to conventional coating whose deisgn life is just between 5 and 15 years.)

Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[SJones]

If the specification says that 316L is not permitted above a certain temperature, then why are you entertaining the thought of trying to protect it with paint? Of course, we can get into debates about whether a valve body is stressed sufficiently to give rise to SCC, and whether painting reduces the risk associated with SCC to an acceptable level simply by reducing the surface area exposed to the environment. The TSA option is more robust and damage tolerant, particularly at elevated temperatures, as well as providing electrochemical corrosion control. It also will not have any embrittlement issues associated with zinc and stainless steel in fire scenarios (another debate that can be had). If you want to use a conventional coating system to cover over an incorrect materials selection, then you have to convince the end user that the risk associated with SCC is acceptable. Good luck with that exercise.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.