Aluminum Casting Porosity Sealing

[Bicky22]

I have some small (4”x4”x2”) porous aluminum castings that I would like to seal for a low pressure application <10 PSI.

I do not have a way to vacuum impregnate these in house, nor do I want to send these parts out at the moment. I have found some 2 part, brush on sealants. (

http://impco-inc.com/#how-it-works)

...But I would also like to avoid mixing and brushing.

Ideally, I am looking for a solution in which I can dip and (temperature?) cure.

Does anyone have any suggestions for me?

 

[Compositepro]

Dipping will require hundreds of times the volume (cost) of sealant compared to brushing and would only be done in a production environment.

When solvents evaporate you get shrinkage, which is not good for creating a seal. Also solvent vapors cause air in voids expand which creates bubbles and pin holes in coatings.

What kind of product will turn from liquid to solid when you want it to, and not in the container without solvent evaporation? A two part reactive material that must be mixed, or a hot-melt.

 

[Bicky22]

Thank you. Very good information!

Let’s assume production environment; do you have any hot-melt suggestions?

 

[TugboatEng]

Loctite 290.

From the data sheet:

I have used it successfully to seal weld porosity at 350 psi.

 

[BrianE22]

We've used:

FP114A from

http://microleak.com/

We just brush it on the interiors of the gearbox castings.

 

[Bicky22]

Thank you both.

I do not understand the reason behind Step 2 of the porosity sealing for Loctite; could someone clarify?
Allow to cool to 85C (then?) apply the product? Or apply the Loctite while the part is at 121C?
I wouldn’t understand the reason behind the former interpretation here; for both heating and cooling the part both before applying the Loctite, but that is how I am reading it. I could understand heating during or after Loctite application.

The Microleak product looks perfect… however it’s been a week of calls and email to the company with no responses.

So, I am still open to ideas.

 

[TugboatEng]

I assume the purpose of heating and cooling is to help draw the product in to the substrate. The product is applied once it has cooled to 85C. If applied hot the 290 would cure before capillary action can draw it deep into the pores.

Honestly I've applied it at room temp and it works just fine.

 

[Compositepro]

The purpose of heating to 121C is to remove any liquid water that may be in the pores. 85C is a safe temperature to apply the adhesive, where it is not too reactive and has a low viscosity. Cooling from 85C will help draw the adhesive into the pore.