You should upgrade or use an alternative browser. Why is a weld often the first area to rust? Thread starter AndyStobbs Start date Feb 11, AndyStobbs Member.
Messages 2, Location North West England. In the course of my job, I'm often on farms, working on farm machinery. Is it because, a the welded area is subject to greatest movement forces, as a weld typically joins pieces of the machine that would tend to pull apart through the forces on them b The finished weld has not been dressed, or in some other way is more likely to hold moisture c The ultimate metal composition is altered, making blistering more likely d Other Moderator Staff member.
Messages 6, Location Northampton. AndyStobbs said:. Ah, makes sense. Messages 1, Location Kendal, Cumbria. Ive noticed this too, any way to prevent it? TechnicAl Banned. Messages 8, Location Rotherham. I think that, if true, its coincidental. Are they welding or burning it.
Some weld a LOT colder than others with excellent results. I have to disagree with Mr. Collins assessment of the decrease in corrosion resistance of the weld heat affected zone. Most of the loss in corrosion resistance for weld HAZ is a near surface phenomenon. The heat from welding does cause surface oxidation and results in a very thin layer of chromium depleted material at the surface.
This thin layer has lower corrosion resistance. This layer, however, is seldom more than a few hundred Angstroms thick and can easily be removed by chemical passivation. Welding supply companies sell chemical treatments specifically for restoring corrosion resistance around stainless steel welds.
The chromium carbide precipitation phenomenon is limited to the grain boundaries of the material - this phenomenon is called sensitization. The loss of corrosion resistance is specific to the material grain boundaries, and is generally not a problem in atmospheric corrosion. Sensitization is usually a problem in specific corrosive environments and is manifested as grain boundary cracking in the HAZ. Switching stainless steel alloys will probably not help either if you don't passivate the weld HAZ.
Be careful with your abrasive cleaning that you don't don't create crevices by local metal smearing or embed abrasive particles. Crevices can be deadly to corrosion resistance of stainless steel.
I apologize for the long winded response, when I could easily have said that I think a good passivation treatment will solve your problems at the welds and in abrasively cleaned areas. Electropolishing would be nice, but may be overkill. I think that nickel plating is also overkill.
I feel Mr. Hanke has his facts correct. Sensitization usually occurs because of an in-service environment and rarely is due to the rapid heating and cooling cycles of the welding operation.
I also think passivation is the answer. Hello, and thanks in advance to anyone who has the expertise, time, and occasion to offer guidance. My name is Tim, and my company makes golf putters. The putters are milled from SS and one of the finishes we offer is a deep gold color achieved from torching the head with a MAP torch. Today I was contacted by a customer who told me his putter was beginning to rust in spots.
The putter was produced in June, but we have sold a bunch over the last year with this same torched finish. The following is copied from an answer to a previous question regarding rust due to welding "Most of the loss in corrosion resistance for weld HAZ is a near surface phenomenon. Also is there a fix that can be recommended and performed on the customer end that will not result in damage of the customer or the product if not executed correctly? It is essential to inspect the weld deposit immediately after the welding process.
For maximum resistance to corrosion, the surface must be smooth, uniformly oxidized and free of irregularities and other foreign particles. Grinding may be used to even out the roughness and weld spatter , while a wire brush may be used to smooth out the surface.
However, brushing is not recommended for stainless steels since it may disturb the passive film and reduce its resistance to corrosion. Using welding consumables such as low-hydrogen shielded metal arc welding electrodes, cleaning the welding surfaces and drying the flux will reduce the presence of hydrogen pickup and hence prevent the associated hydrogen-induced cracking. A protective surface coating applied to the welded joint as well as the parent metal minimizes the chances of localized corrosion, which may arise due to the variations in the weld metal composition.
The treatment reduces the residual stress gradients and is an effective method of reducing the susceptibility to stress corrosion cracking. The PWHT reduces the composition gradients and the formation of microgalvanic cells.
The other role of the treatment is to transport hydrogen from the weld regions and hence prevent hydrogen cracking. Corrosion in welds may occur due to several contributing individual factors or a combination of factors. The effects of these factors can be minimized through the appropriate selection of materials and welding procedures.
Stress-relieving after welding, slag removal, avoidance of crevices, sharp notches, rough finish and galvanic couples are some of the main preventive measures that can minimize the possibility of corrosion in welds. Written by Kasay Mwiks. Subscribe to our newsletter to get expert advice and top insights on corrosion science, mitigation and prevention. By: Della Anggabrata. Dictionary Dictionary Term of the Day.
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