welding manganese phosphate coated steel?

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This is a strange one. I figured if you guys don't know, who would.I have a bunch of steel to weld that has chemical conversion coating of manganese phosphate. The surface has a dark greyish color. I was told this makes a good base for paint or for retaining oil.I tigged a few pieces together, without even grinding off the phosphate, and got nice looking welds. The amperage needed to be a touch higher but otherwise I wouldn't have even known it was there. The coating is micro thin I guess.Is this is a bad idea? Are there any strength issues with manganese phosphate in the weld? Also, how bout fumes? Toxic? I do know that its NOT zinc phosphate, made sure of that before setting into it.Clearly I don't know much about this except the customer wants the coating on. (Yeah, they could have done the coating after all the welds but the metal had to fit in a tank..).Help me oh welding gurus..
Reply:Well, one thing is sure. Once welded, those areas are not coated anymore!!! As for the welding, the coating is very thin, and when it is melted, ther is very little if any retention in the steel. So- not really much chance for contamination of the weld. You are good to go. As a primer, look to a zinc phosphate or zinc cromate to protect the welds from rust. It is used primarily in marine and aeronautics. Both will match the job of the phosphate coating, and take paint very well.
Reply:I appreciate it, thanks. Nice to know that what looks like a good weld actually is.I didn't notice any fumes, but does this require precautions? Not much worried about myself  but I'm working indoors with other folks aroundI'll have to get some of the primer you mentioned too
Reply:If this material is for a government contract, you may want to check with the customer before adding any additional primers/protective coatings.  The stuff you are describing sounds like the base for CARC (chemical agent resistant coating).  That phosphate coating is essential to the effectiveness of the coating and the ability of that piece to be decontaminated after exposure to chemical agents.
Reply:myself?if i have any doubts what so ever i just hit it with the grinder where the weld is going untill i see bare metal..its always good to start with clean bare metal anyway.......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.