Posted by Keith in Washington on Wednesday, May 03, 2006 at 12:53PM :
In Reply to: sealing up pinholes in oil pan posted by jim in n.y. on Tuesday, May 02, 2006 at 8:57PM :
You did not say how or where the pin holes are happening. The pin holes are most likely caused by impurities/contaminations in/on the metal. Make sure that the metal is really clean. Grind and or wire brush it very well. Being an oil pan I suspect that some oil has "soaked" into the metal. I suspect since you have pin hole that you are getting a lot of splattering when you are welding which are the impurities coming out of the metal (I hate those little volcanoes).
I have found that when I can not get a good weld it is most often due to metal that is not clean. Recleaning it usually solves the problem. With sheet metal I usually use an abrasive pad (can not remember what they are called) on my grinder. They really give you a clean surface. Much better than a wire wheel or brush.
I have also run into metal that just will not weld cleanly. It is ually older used metal. It, as best I can tell, the metal had significant impurities when new or was cantaminated during use. Cleaned up rusted metal also seems to cause problems with wire or TIG welders.
Make sure that your welding material is clean. I find either gas wire feed or TIG welders are best on sheet metal. I do not care for flux wire feed welding. With TIG make sure your tip is spotless.
If you are stich welding an inch or so at a time to prevent the pan from warping, make sure that you are overlapping the welds as you will get pinholes at the joints.
I have never brazed. But once you have brazed it, it is about impossible to weld the joint. The brazing is a contaminant as far as welding is concerned. It is also difficut to clean it off it you want to weld.
Hope this helps.