Field Coating for Aluminum Bridge Railing 1

[whatname]

I have a client who, as part of a bridge repair project, would like to have the aluminum railings cleaned and/or coated.

The railings are constructed of uncoated aluminum, either 6061-T6 or 6351-T5. They are approximately 50 years old. The client would like to remove the heavy layer of oxidation from the surface.

If I were to specify that the railing be cleaned by say, soda or bead blasting, it's my understanding that the aluminum would immediately begin to oxidize again. How long would it be before the oxidation became visible and begin to dull the sheen of the railing? If it were, say, more than a year, the client may be satisfied with just cleaning it and calling it a day. If much quicker, could a clear coating, such as a urethane or similar product, be applied to prevent the immediate re-oxidation.

I'm concerned about using a coating such as a urethane for a number of reasons: Would it be difficult to field apply at the correct thickness? Would it prone to peeling? After a few years (assuming the coating lifespan of 3-5 years) would the aluminum begin to oxidize normally, or would the client need be committed to continue re-applying the coating?

Note: The railing cannot be removed from the bridge to be shop cleaned/coated.

Thanks.

 

[unclesyd]

Depending on the driving force of your oxidized Al you may have a pitted surface under the oxide and the only way to remove it is to blast it away with soda if this allowed.

Again depending on how heavy your oxidation is you might look at Aluminum Bright from JMN. Under the right conditions this type material can be quite effective. It should leave a very light phosphate conversion coating on the Al that will impede the formation of more oxide.

The second link is to a different type Al cleaner that will leave only the base metal surface and will do nothing to impede the reformation of an oxide. You might want to force a clear phosphate coating on the base metal.

I would give both companies a call to discuss your problem and if their products are worth a test.

Depend on the required results, dull, shinny, or polished there are approaches available to accomplish the job. You might have to lightly blast the Al and then use a brightener or wash primer if you are going to coat the Al. There is also the conversion coatings that will greatly impede the formation of new oxides. the only problem is you will have a variegated finish as the final result.

What type of final finish is required on the Al?

http://www.abrite.com/fralumpretre.htm

http://www.jmnspecialties.com/artic...luminum-cleaners-acid/67-aluminum-bright.html

 

[whatname]

Thanks for your reply. I will call the companies you referenced to discuss it with them.

The client is not overly concerned with the sheen of the finish; the goal is to prevent visible oxidation for at least several months so that the Al appears to have been attended to as part of the overall bridge repair project.

 

[CoryPad]

You can coat aluminium. Contact professionals if you do not have the requisite experience, equipment, etc.

Consider using a pretreatment, such as Henkel's Alodine, combined with a coating. For full corrosion resistance, a base layer of epoxy plus a top layer of urethane would provide excellent results.