Q. I am ashamed to have to ask this question since I worked in a physical workshop 30 years ago. I will place one corner of the patch panel cab on my F-150, using both MIG spot welders and resistance welders. I will butt the upper part and weld the factory seams. I'll use a solder primer, but how do you best seal the joint on the back of the cabin? We used to put some putty on the edge, but what do you recommend?
James C. Gibson
By email
A: There are a variety of "joint sealants" designed exclusively for this purpose. Every car paint business has professional quality products and there are many good online providers. The use of these seals is a very good way to prevent the ingress of moisture between the metal layers, which can lead to rust problems on the road.
Here are some tips that can help you with the careful use of these products. After cleaning the seal, place two strips of tape at a distance of about 2.5 cm (centered on the joint). Then you can generously apply sealant. Remove the tape before the sealant cures, and you will get a clean and beautiful edge of the seal. You can further smoothen the sealant by gently brushing it off with a solvent-soaked brush.
Do not use any household products for sealing, as these are not intended to seal metal seals on vehicles.
Q: I recently purchased an imported TIG welder and I have a lot of porosity issues with my welds. I use the same steel filler bar that I used with my old autogenous welder and get very good results. Do you think they sent me a broken machine?
A: Although there may be a problem with your welder, it is unlikely to be the cause of your porosity problems. There are many things that can cause porosity in TIG welding, but first I want to see the welding rod that he uses. The most common type of rod for gas welding of steel is RG-45 or RG-60. They are NOT designed for TIG welding! The TIG process is very complex and the best bars are carefully deoxidized to optimize for inert gas welding. For TIG welding, an ER70S rod must be used. There are a few variants of this rod, -2 and -6 are the most common, but each element of the "family" ER70S will work well for you. Do yourself a favor when buying a dipstick and buy it. It's MUCH better to weld body parts than the 1/16 inch rod you've probably used for gas welding.
Some other common problems that can cause porosity are not enough argon or keeping the burner pot too far from the base metal. You should ONLY use direct argon. The argon-CO 2 mixture used in MIG welding does NOT work for TIG welding.
Any type of contamination in base metal can also lead to porosity. You must clean the metal with a good degreaser to remove the oil or grease BEFORE using abrasives to remove the last traces of rust, corrosion, paint or other contaminants. If you grind an oily metal, impurities settle in the joint, which makes cleaning very difficult.
There's a good chance these simple steps will solve your problem, but contact me again if the issues persist. The TIG process has many advantages over the oxyacetylene process. I hope you enjoy the full potential of your new machine!
You can email your questions to Professor Hammer ( covell@cruzio.com ) or email Covell Creative Metalworking, 106 Airport Blvd, Suite 105, Freedom CA 95019. You will receive a personal answer. Ron Covell has made many metallurgical videos. Now you can STREAMED or DOWNLOAD from your website! And check them out in covell.biz's ongoing series of workshops across the country, or request an updated program of workshops and a free DVD catalog. Telephone (831) 768-0705. You can also watch Ron's YouTube channel: www.youtube.com/user/covellron .
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