MolaKule
Staff member
ZDDP and Detergent Interactions during Run-In
Tech Brief by Molakule
A recent paper in the July 2003 issue of Lubrication Engineering* presented some interesting data on the subject of ring/cylinder tribological interactions during run-in, or "breaking-in." Also a member of the BITOG board has asked for a summary of that paper, and due to its timely association with recent topics here, we will offer a summary.
Objective:
The authors of the paper wanted to know what type of additive elements would show up on the surfaces of rings and cylinders during run-in, and to determine the "competitive adsorption" between ZDDP and detergents; something we generally call, 'uptake.'
Description of Testing and Analysis System (Tribotester and Analysis Machines):
The testing apparatus was an SRV tribotester. Basically, this is device that uses a clamp to hold a piece of piston ring against a lower specimen, the lower specimen being a curved piece of metal of cast iron, which simulates the cylinder. The mechanism moves the clamped piston ring back and forth on the "lower specimen" in an oscillating fashion, simulating the rubbing motion of the ring/cylinder contact surface.
The analysis machines were Energy Dispersive X-Ray Analyzers (EDX) and IR spectrum analyzers. The EDX could scan the surfaces of the rings and cylinder, and determine basic elemental makeup of the rings and cylinder. The IR spectrum analyzer was a Bio-Rad Oil Analyzer used to analyze the "VOA' of the oil. After the test, an Auger Electron Spectroscope was used to determine what elements resided on the ring and cylinder surfaces after break-in. The amount of "preferential adsorption" or elemental 'uptake' could then be determined.
Materials Used:
The oil used was an API SJ rated, SAE 5W30 mineral oil with ZDDP (or ZDTP), and magnesium and calcium Dispersant /Detergents. The elemental analysis of the oil was:
Mg - 228 ppm
Ca - 596 ppm
P - 919 ppm
Zn - 1082 ppm
S - 5060 ppm
Si - 2.1 ppm
The cylinder liner material was cast iron consisting of 93.3% iron, 0.4% Chromium, 3% Carbon, and 1.3% manganese. Three different types of rings were used: A chromium plated ring, a Moly coated ring (base material consisting of nickel-chromium-boron-silicon), and a Nitrided Stainless Steel ring.
Results:
Rings:
The rings showed a greater affinity or uptake to ZDDP over the detergents Magnesium and Calcium. Overall, the surface activity with ZDDP ranked this way (in decreasing order), Fe/Mol>Fe/Cr>Fe/Nitrrided.
The Moly coated rings showed the greatest affinity to the elements (in decreasing order).
S>P>Zn and the least affinity to detergents. It showed the greatest affinity to ZDDP.
The Chromium plated ring showed affinity toward the elements (in decreasing order),
P>S>Zn and the median affinity to the detergents. It showed a median affinity to ZDDP.
The Nitrided rings showed the greatest affinity to the elements (in decreasing order).
P>S>Zn, and the greatest affinity to detergents. These ring showed the least affinity to ZDDP.
Cylinder Liner:
The cylinder liners showed more adsorption of ZDDP over detergents than even their ring counterparts.
Summary:
So what are the investigators try to learn? What elements from critical additives compete for the surfaces in partial to boundary lubrication regimes.
What can be learned from this study?:
We can determine the optimum balance of additive in the add package in order to optimize the ratio of AW to DD additives, in order to derive the least wear with the most cleanliness in the piston/cylinder area.
What I would like to see in these types of studies:
I do wish they would continue this study into the areas of Moly DTC, Boron, and Antimony DTC AW/EP additives to determine what chemical elements are the MOST preferential to rubbing surfaces such as rings/cylinders in the boundary lubrication regime.
*Competitive Surface Interactions of Critical Additives with Piston Ring/Cylinder Liner components on Lubricated Breaking-in Conditions, Lubrication Engineering, July 2003, pp. 10-15.
[ August 06, 2003, 04:24 PM: Message edited by: MolaKule ]
Tech Brief by Molakule
A recent paper in the July 2003 issue of Lubrication Engineering* presented some interesting data on the subject of ring/cylinder tribological interactions during run-in, or "breaking-in." Also a member of the BITOG board has asked for a summary of that paper, and due to its timely association with recent topics here, we will offer a summary.
Objective:
The authors of the paper wanted to know what type of additive elements would show up on the surfaces of rings and cylinders during run-in, and to determine the "competitive adsorption" between ZDDP and detergents; something we generally call, 'uptake.'
Description of Testing and Analysis System (Tribotester and Analysis Machines):
The testing apparatus was an SRV tribotester. Basically, this is device that uses a clamp to hold a piece of piston ring against a lower specimen, the lower specimen being a curved piece of metal of cast iron, which simulates the cylinder. The mechanism moves the clamped piston ring back and forth on the "lower specimen" in an oscillating fashion, simulating the rubbing motion of the ring/cylinder contact surface.
The analysis machines were Energy Dispersive X-Ray Analyzers (EDX) and IR spectrum analyzers. The EDX could scan the surfaces of the rings and cylinder, and determine basic elemental makeup of the rings and cylinder. The IR spectrum analyzer was a Bio-Rad Oil Analyzer used to analyze the "VOA' of the oil. After the test, an Auger Electron Spectroscope was used to determine what elements resided on the ring and cylinder surfaces after break-in. The amount of "preferential adsorption" or elemental 'uptake' could then be determined.
Materials Used:
The oil used was an API SJ rated, SAE 5W30 mineral oil with ZDDP (or ZDTP), and magnesium and calcium Dispersant /Detergents. The elemental analysis of the oil was:
Mg - 228 ppm
Ca - 596 ppm
P - 919 ppm
Zn - 1082 ppm
S - 5060 ppm
Si - 2.1 ppm
The cylinder liner material was cast iron consisting of 93.3% iron, 0.4% Chromium, 3% Carbon, and 1.3% manganese. Three different types of rings were used: A chromium plated ring, a Moly coated ring (base material consisting of nickel-chromium-boron-silicon), and a Nitrided Stainless Steel ring.
Results:
Rings:
The rings showed a greater affinity or uptake to ZDDP over the detergents Magnesium and Calcium. Overall, the surface activity with ZDDP ranked this way (in decreasing order), Fe/Mol>Fe/Cr>Fe/Nitrrided.
The Moly coated rings showed the greatest affinity to the elements (in decreasing order).
S>P>Zn and the least affinity to detergents. It showed the greatest affinity to ZDDP.
The Chromium plated ring showed affinity toward the elements (in decreasing order),
P>S>Zn and the median affinity to the detergents. It showed a median affinity to ZDDP.
The Nitrided rings showed the greatest affinity to the elements (in decreasing order).
P>S>Zn, and the greatest affinity to detergents. These ring showed the least affinity to ZDDP.
Cylinder Liner:
The cylinder liners showed more adsorption of ZDDP over detergents than even their ring counterparts.
Summary:
So what are the investigators try to learn? What elements from critical additives compete for the surfaces in partial to boundary lubrication regimes.
What can be learned from this study?:
We can determine the optimum balance of additive in the add package in order to optimize the ratio of AW to DD additives, in order to derive the least wear with the most cleanliness in the piston/cylinder area.
What I would like to see in these types of studies:
I do wish they would continue this study into the areas of Moly DTC, Boron, and Antimony DTC AW/EP additives to determine what chemical elements are the MOST preferential to rubbing surfaces such as rings/cylinders in the boundary lubrication regime.
*Competitive Surface Interactions of Critical Additives with Piston Ring/Cylinder Liner components on Lubricated Breaking-in Conditions, Lubrication Engineering, July 2003, pp. 10-15.
[ August 06, 2003, 04:24 PM: Message edited by: MolaKule ]
