Acid causing welded joint to weaken

By Inertialabs Date 12-08-2014 03:53

I just had a weld fail on a machine that I make , The failed joint was 1" thick 6061 aluminum plate and the with a 4.5" OD 6061 1/2 wall pipe butted into it
I ran a 90 degree tack pattern 4 tacks 3/8 long and the weld is a 3 pass weld using a 4043 3/64 filler wire weld. I have pictures showing the inside of the joint
after failure and it appears that there was a huge amount of corrosion inside the weldment. I am guessing that the weldment was not properly plugged and or
flushed after anodizing. The anno process is a hard black type III mil spec finish. Can someone explain if the acid reaction is causing strength issues and describe
what is happening ? :confused:

By welderbrent (*****)

Date 12-08-2014 18:15

Inertia,

WELCOME TO THE AWS WELDING FORUM!!

Now that you have posted you can look at the bottom of your post and see the 'Attach' button. Use that to browse your pics and attach the photos for our viewing.

Next, what was the length of time between anodizing and failure?

And, for clarification, are we talking about GTAW with filler rod or GMAW with filler "wire"?

Oh, and how about welder settings and gas shielding?

Just trying to cover all bases.

He Is In Control, Have a Great Day, Brent

By Superflux (****)

Date 12-08-2014 18:20

Inertialabs,

I just spoke to my resident anodizing expert and was informed that if all the chemicals are not boiled, flushed and Completely cleaned, then the residues left in the unwelded faying surfaces could create the failure you have described.
Considering the close dimensions involved, perhaps some form of "Resist" could be applied to prevent the entrapment of the chemicals in the open side of the weld joint.
I would talk to your anodizor for suggestions.

Oh yes and please post those fotos.

By Inertialabs Date 12-09-2014 17:12

Superflux, thanks for the info

The weldment is really bad for trapping liquid , last night I drilled out a hole so I could insert a small video camera inside the joint and found a small amount of liquid
not sure what it is so I need to talk to the platter and find out how to test for acid vs water. Oh I also found a pile of aluminum chips ;)
I am supposed to have another conversation with the platter today so I will update this once I have more information

Here are some pics of the broken weld and also the new one I described

Attachment: plate.jpg - broken weld (95k)

Attachment: x.jpg - broken weld (21k)

By 803056

Date 12-12-2014 16:47

You can get Litmus paper from a number of scientific suppliers. It isn't expensive and it isn't difficult to buy. The names Welch, Fisher, Edmond, come to mind.

I purchased some Litmus paper for my grandchildren so they could "test" different foods found in the refrigerator to see what foods were acidic and which were bases. It cost more for postage than for the actual product.

Acids are going to cause most metals to corrode. The design should factor that in to the design ensure the design doesn't include "traps" that will retain corrosive materials such as acidic or alkaline residues (very corrosive to aluminum alloys).

Best regards - Al