What is the suggested nitric acid and phosphoric acid ratio for CIP?
We had been using a nitric acid / phosphoric acid cleaner that was stated on the SDS as phosphoric acid 10% - 25% by weight and nitric acid in the same range 10% - 25% by weight. Out of the blue our chemical supplier informed us that they would be switching us to a new product, the new one is stated on the SDS as phosphoric acid 1.0 - 10% by weight and nitric acid 10% - 25% by weight. This is used for CIP of steel dairy equipment, after dilution. My concern is that the ratio of the 2 acids will now be different, leaning more towards the nitric. Is there an ideal ratio between the two and is our supplier doing this to save money at our expense? The price is unchanged.
I would start by asking your supplier these same questions.
Out of curiosity I looked at other CIP products and their ratios.
AEB ACID CIP Nitric Acid= 20-30% Orthophosphoric Acid= 1-5%
I even found one that says phosphoric acid as low as 0.5% is effective.
(Y. Chisti, in Encyclopedia of Food Microbiology, 2014)
https://www.scienced...in the industry.
Here is another link to some interesting reading- focused on brewing systems though. This mentions phosphoric acid may react with rubber gaskets.
Maybe this is the reason for the switch? There's only one way to know for sure.
Using 2% Nitric acid solution is also advisable.
I don't think that you will find that there is any consensus the ratio X:Z is the most optimal. Which acids and ratios can be dependent upon the application.
With that said, how does the dosing change? If you now have to use more chemical to achieve the same results, then yes it could be a clever way of disguising a price increase. Or on the more optimistic thought process, it could be them trying to find you a less inexpensive product, equally effective product as to not pass along a price increase / keep your costing the same. I guess what reasoning they give for the change may help discover their motives.
Are they going to help you with revalidation of the CIP system? At the least you still have that task to consider as well.