Highflight
Well Known Member
I was contacted by Jon at Sanchem who felt that the Sanchem 6100 product is being a little misunderstood here on the RV forum. Based on his comments, he might be right so I thought I would pass on his notes here.
However, I'd like to start backwards and mention something that has been brought up before and something that I also have never been comfortable with when using the acid wash type systems (ex. Alodine).
Allow me to cut and paste from another message in this forum (from George Goff) that explains this issue:
gvgoff99 Join Date: Jan 2005
Location: Houston, TX
Posts: 44
Another consideration BEFORE you Alodine
I want to thank you Vern for an excellent and informative article. I also wanted to add the following that I found about the Alodine process. This is under the technical information at: http://www.alphametal.com/index.html
"Anodizing Aluminum assemblies
Aluminum parts that have been assembled together will anodize successfully. However the designer should be aware that lap joints such as spot welds and joints that are not completely watertight can become traps for cleaning agents and sulfuric acid. In some cases it is impossible to completely rinse all of the sulfuric acid from the joint. If this happens the joint then becomes a site of increased corrosion potential............. . However, as above, it is much better practice to consider this potential problem during the design phase of your product and plan to do the anodizing before assembly if at all possible. "
This information and Vern's information about the self-etching primers has saved me a lot of work. I found the above information as the result of a search that I did when I was wondering about the acid that almost for sure is held in by capillary action around the seams and rivets when doing the acid wash during the alodine process.
__________________
George Goff RV-6A (Houston, TX)
As George points out, it is possible that you can actually cause corrosion when prepping an assembled fuselage or wing because of wicking into lapped areas that cannot later be properly rinsed and neutralized.
So to better clarify this issue specifically with regard to Sanchem 6100, I asked John at Sanchem to explain the difference between the 6100 and other acid wash systems. I have cut and pasted my question and his answer below.
Jon,
When using the chemical wash treatments, I have never been comfortable with the idea that the acidic wash can wick into really tight areas (seems, etc.) where they can't be properly rinsed. That can actually CAUSE corrosion problems in the very areas that you are trying to protect.
So my question is; is the Sanchem 6100 similar where it could cause a problem in areas that can't be rinsed, or is the chemistry of the 6100 different where wicking isn't a problem?
I know that there's no problem when using 6100 on whole, unassembled panels, but many people buy "QuickBuild" kits where major areas of the aircraft are already riveted together. Should those people avoid using the 6100 in those circumstances?
Thanks,
Matt
Matt
Chemical wash treatments use a very strong acid that is designed to cut into the surface of the metal in order to “anchor” the coating to the metal’s surface. The acid used in “6100C, Mild Acid Cleaner” is a very mild acid that is not able to cut into the surface of the metal. It is only designed to loosen surface dirt so it can be rinsed off. In addition the “Safegard 6100” conversion coating, which is applied after cleaning the metal surface, will neutralize any acid it comes in contact with.
Jon[/I]
I thought this tidbit might be of interest to those who are thinking of using an acid wash pre-prep on their assembled aircraft.
However, I'd like to start backwards and mention something that has been brought up before and something that I also have never been comfortable with when using the acid wash type systems (ex. Alodine).
Allow me to cut and paste from another message in this forum (from George Goff) that explains this issue:
gvgoff99 Join Date: Jan 2005
Location: Houston, TX
Posts: 44
Another consideration BEFORE you Alodine
I want to thank you Vern for an excellent and informative article. I also wanted to add the following that I found about the Alodine process. This is under the technical information at: http://www.alphametal.com/index.html
"Anodizing Aluminum assemblies
Aluminum parts that have been assembled together will anodize successfully. However the designer should be aware that lap joints such as spot welds and joints that are not completely watertight can become traps for cleaning agents and sulfuric acid. In some cases it is impossible to completely rinse all of the sulfuric acid from the joint. If this happens the joint then becomes a site of increased corrosion potential............. . However, as above, it is much better practice to consider this potential problem during the design phase of your product and plan to do the anodizing before assembly if at all possible. "
This information and Vern's information about the self-etching primers has saved me a lot of work. I found the above information as the result of a search that I did when I was wondering about the acid that almost for sure is held in by capillary action around the seams and rivets when doing the acid wash during the alodine process.
__________________
George Goff RV-6A (Houston, TX)
As George points out, it is possible that you can actually cause corrosion when prepping an assembled fuselage or wing because of wicking into lapped areas that cannot later be properly rinsed and neutralized.
So to better clarify this issue specifically with regard to Sanchem 6100, I asked John at Sanchem to explain the difference between the 6100 and other acid wash systems. I have cut and pasted my question and his answer below.
Jon,
When using the chemical wash treatments, I have never been comfortable with the idea that the acidic wash can wick into really tight areas (seems, etc.) where they can't be properly rinsed. That can actually CAUSE corrosion problems in the very areas that you are trying to protect.
So my question is; is the Sanchem 6100 similar where it could cause a problem in areas that can't be rinsed, or is the chemistry of the 6100 different where wicking isn't a problem?
I know that there's no problem when using 6100 on whole, unassembled panels, but many people buy "QuickBuild" kits where major areas of the aircraft are already riveted together. Should those people avoid using the 6100 in those circumstances?
Thanks,
Matt
Matt
Chemical wash treatments use a very strong acid that is designed to cut into the surface of the metal in order to “anchor” the coating to the metal’s surface. The acid used in “6100C, Mild Acid Cleaner” is a very mild acid that is not able to cut into the surface of the metal. It is only designed to loosen surface dirt so it can be rinsed off. In addition the “Safegard 6100” conversion coating, which is applied after cleaning the metal surface, will neutralize any acid it comes in contact with.
Jon[/I]
I thought this tidbit might be of interest to those who are thinking of using an acid wash pre-prep on their assembled aircraft.
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