Hello Alex, I'm no expert, so I can't lead you to any specific code section to support your train of thought. I have read in different threads on different occasions of the requirements to remove surface contaminants, rust, mill scales, paints(I believe), and any other detrimental surface conditions. You may be able to argue an inference of the code that since you have tested weld samples with the paint included and they have successfully passed this testing, that this is not a detrimental condition and thus should be allowed. I would venture to say that others with more specific code knowledge here on the forum will soon chime in and give you a more concrete and supportable answer, one way or the other. I look forward to those additional replies also. Best regards, aevald

You may be thinking of 5.15 in D1.1.  That does not outright say it is OK to paint the groove surfaces- rather it says that foreign material that would cause problem is not acceptable.  Your testing indicates paint is no problem so paint in the weld zone might be allowed by infererence.

It is admirable that you have conducted testing to show your paint doesn't cause problems.  However other parts of D1.1 lead us to understand that we should be sure there is NO paint, dirt, oil etc in the weld zone.  I can see that you will continually have difficulties in getting engineers to accept your testing because including paint goes against common perceptions.

I am curious, does your testing indicate the type of paint and the maximum allowable thickness of paint?  Those will be significant variables.

The code does not speak much of this item, but there is a provision in which you can set criteria for acceptance on the basis of evidence engineering.
Section 6 Reference 6.8.

Greetings

Erik

I agree that AWS D1.1-2006 paragraph 5.15 includes the weasel words "a thin rust-inhibitive coating, ......, may remain with the following exceptions, ....."

The aluminum based paint mentioned in this thread has been used as a rust inhibitive coating for many years. If it is truly thin and completely dry, it comes off easily with a hand brush. The fact that it contains a high percentage of aluminum can be "beneficial" in that any residual aluminum is an effective deoxidizer. The problems that can be encountered include the mind set that "if a little is good, more must be better" and a very heavy coating is applied to the surfaces to be welded. Another consideration that has to be factored in is whether the "rust inhibiting coating" (paint) is completely dry when it is time to weld. If the paint is not fully cured the liquid vehicles in the paint can be considered as contaminates that can result in increased amounts of diffusible hydrogen and porosity. 

You can't beat a joint that is free of all contamination if you are optimizing the weld quality, but that is not always necessary. If optimum quality was required, the acceptance criteria included in D1.1 or the other welding standards would be more stringent than they are. Have you ever read the acceptance criteria of API 1104? Imagine, cross country pipelines with incomplete joint penetration, porosity, crater cracks, whiskers and the multitude of other discontinuities that would be considered as defects by many other welding standards.

You heard it here first folks, API has relaxed the X-ray standards; now if the beam of light from a flashlight can not pass through the welded joint, it's acceptable. Just kidding fellas, I just wanted to stir the water and see the mud swirl around a bit. Let the hair that is standing up on end settle down, relax, relax, relax. There, all better. :) I'm glad some of you can't reach me through the computer screen!;)

I guess the point I'm trying to make is that welding standards include acceptance criteria that provide a level of quality consistent with the design assumptions. Some welding standards include several different acceptance criteria for different applications, operating temperatures, operating pressures, or unit stress allowables and safety factors. Our job as welders and inspectors is to ensure the required quality level is met.

To paint or not to paint, that is the question. This isn't rocket science. If the steel is to be stored in the field for a while before being erected, would I rather remove rust or a rust inhibitive coating? I favor the silver paint stuff any day of the week. It is easier to remove than rust. A little preheat, a quick pass or two with a wire brush to remove any residual aluminum paint and the joint is ready for welding.

Have a Happy Holiday and a Merry Christmas!

Best regards - Al

  I too agree that D1.1 section 5.15 is a bit "vague" . However section 8.5.1 is rather clear. Short story. We were working a mass transit project in which the paint was to be "welder friendly" It turned out to not to be the case. The EOR dictated that 8.5.1 is how parts were to be prepared. Personally, if I am signing off on a weld, I would prefer to see the prep done to 8.5.1....     Just my .02.  Merry christmas all!!

Food for thought, How would this fly with OSHA? If qualified and proven then I would say, in my opinion it would be acceptable, with documentation, from a quality standpoint. However, to put this proceedure in action, you may have a fume and ventilation issue. When you open the "respirator" door it can be a monster. Fit tests and the likes, as well as upkeep of respirators.

AWS D1.1 index, "paint removal" refers you to 5.15 and 8.5.1 for welding purposes and 6.26.3 for inspection. 6.26.3 does not apply to this issue. My interpretation of the other two is this. Paint is a foriegn material detrimentel to weld quality and AWS does imply this by thier referance in the index as " Paint removal" and above mentioned references to 5.15 and 8.5.1 These two references when read in thier entirety and applied is stated should give one the determination that paint shall be removed two inches in all directions from the weld area.