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Manganese Phosphate Coating

Q. HELLO TO WHOM READ THIS. I am R.Farhangi and now want to know some information about Mn phosphate coating on the some parts of the engine, and effects of adding NO3 and Cu and Ni to phosphate solution. I will be very glad if someone helps me and sends me any useful data . thanks R.Farhangi


A. A finely crystalline Mn phosphate coating aids the "running in" of engine components. The coating must be fine and allowances made for any alteration to the tolerance of fit. Manganese phos solutions contain 3-6 g/l Mn, 1-3 g/l NO3, obviously phosphate and < 1g/l Ni. Ni is preferred to Cu.

typical operating conditions are 5-15 mins at 95 deg C at 60 points (10 ml sample, 0.1N NaOH, phenolphthalein [affil link] indicator). The solution should contain at least 1 g/l Fe 2+ and percentage free acid 10-15% (ratio FA to TA or pointage).

Unless you are using solvent degreasing you will need a special manganese phosphate refining predip to obtain fine crystalline coating after alkali cleaning. The nitrate and Ni accelerate the process, without Ni you will need 30+ minutes and coating will be too thick! R

Roger Bridger
Walterisation (UK) Ltd - Croydon, UK

Controlling the FA and TA in a Manganese Phosphate Tank

Q. I have recently been asked to take control of the manganese phosphating tank in our workshop. Because I have no previous knowledge about manganese coatings I would like to know how to control the TA and FA levels in the tank. What to do when either is high or low, also what to do when you have fluctuating IP levels. I have to deal with differing metals from 4130 to 4145 with high KSI"s

Nigel Smith
Metallurgical Inspector - Adelaide
March 21, 2015

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