DAlbertson
Electrical
- Apr 1, 2006
- 24
I've started a small design company, and I have 3 corrosion questions on my first product.
It is a mechanism about 1/2 the volume of a can of Coke. The parts are made of the following materials:
1) 260 Brass
2) 410 Stainless, powdered metal, 85% density
3) several different polymers
4) Copper (nearly pure), powdered metal, 94% density
5) Aluminum (Al 91.5%, Cu 2.5-5%, Mg 0.2-0.8%, Si 0.5-1.2%), powdered metal, 90% density.
The working environment is indoors in a non-air-conditioned room surrounded by normal, breathable room air. At times, the ozone concentration in the room may be higher than normal.
My questions are:
1. My understanding is that, in the environment described above, ordinary 410 stainless can develop surface corrosion but that the corrosion will not go beyond the surface layer. Dark spots can appear on the surface, but progressive oxidation and disruption of the surface finish will not happen. Is this also true for an 85% density sintered powdered metal version of 410?
2. Because the equipment is not designed to be run in wet environments, much less in seawater, I was not worried about the materials relative positions on any of the galvanic series. Recently, an associate advised me that I should be concerned about galvanic corrosion, especially given the higher than normal ozone concentration. I just don't know how to evaluate this. Should I be concerned about galvanic corrosion under these circumstances?
3. Aluminum's "self-healing" oxide layer protects the sub-surface from corrosion, although I believe this is more true for pure aluminum metal than most of the alloys. I have seen mechanical mechanisms made of aluminum or an aluminum alloy that have stopped working because of an excess of corrosion. The aluminum surfaces can become very rough, and a white hard powder forms. Would someone tell me how to select an aluminum alloy so that it will not corrode in the environment I've described?
I appreciate any light you can shed on these questions. Thank you very much!
Dave
It is a mechanism about 1/2 the volume of a can of Coke. The parts are made of the following materials:
1) 260 Brass
2) 410 Stainless, powdered metal, 85% density
3) several different polymers
4) Copper (nearly pure), powdered metal, 94% density
5) Aluminum (Al 91.5%, Cu 2.5-5%, Mg 0.2-0.8%, Si 0.5-1.2%), powdered metal, 90% density.
The working environment is indoors in a non-air-conditioned room surrounded by normal, breathable room air. At times, the ozone concentration in the room may be higher than normal.
My questions are:
1. My understanding is that, in the environment described above, ordinary 410 stainless can develop surface corrosion but that the corrosion will not go beyond the surface layer. Dark spots can appear on the surface, but progressive oxidation and disruption of the surface finish will not happen. Is this also true for an 85% density sintered powdered metal version of 410?
2. Because the equipment is not designed to be run in wet environments, much less in seawater, I was not worried about the materials relative positions on any of the galvanic series. Recently, an associate advised me that I should be concerned about galvanic corrosion, especially given the higher than normal ozone concentration. I just don't know how to evaluate this. Should I be concerned about galvanic corrosion under these circumstances?
3. Aluminum's "self-healing" oxide layer protects the sub-surface from corrosion, although I believe this is more true for pure aluminum metal than most of the alloys. I have seen mechanical mechanisms made of aluminum or an aluminum alloy that have stopped working because of an excess of corrosion. The aluminum surfaces can become very rough, and a white hard powder forms. Would someone tell me how to select an aluminum alloy so that it will not corrode in the environment I've described?
I appreciate any light you can shed on these questions. Thank you very much!
Dave
